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TDA8765 10-bit A/D converter demonstration board

1. LNP _ Cbal Rbal2 4 Le onm 00 M amu cr hall nF 08 kasz a Hee ar E EDU 3920 14 16 18 15 psi Rast2 E 22uF ksr Dz SLPE LN gt 7 5 A ESI 1 EXSI OW HEC IR 1N4004 1000F ojo 10 es T ge VBB 4 Cvbb 100 pl E Rastl 470 uF 130kQ 777 GND 19 077 VDD VDD Cvdd 15 44 MEZ uE GND AX 4 29 AUXO T100 nF m o GNDTX ine cd T T2320 nF MELI 20 1 ST2 Ch MICS HFRX 3C 1 isi Cfeed 35 100 nF il a RECO TT 47nF 200kQ i 34 L Rmicp GARX t LnF 1X9 cu Rix 31 wace Cer 1 nF HMICP 100 100 pF Cear sq 22nF 15 33 Cmich Rtx3 TEA1099 QR EARP 7 33 nF 8 2kQ 10 uF 1 C6 33 Ctxl Rtxl 30 MIC aar HMICM 11 amp 22nF 15 GALS SENE 2c Rmicm 2 04 um m 22 EARM EN gals _ _Cgals I nF 1 kQ Lo T 150 pF EA Ctax Ed 43 12 7 m 43 IL o TXAUX LSAO LSOP TAXI n 100 nF Cmf 32 23 vol DTMF VOL 1 100 nF cu 22 VBB 47 9 LSOM 26 8 Ev eee 3 HFTX DLC I R10 txour nk 27 BER CINES m Catx Rgatx GATX n NOT MICS oz 30 1kQ 2 HOO EQUIPP
2. 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 RAUX Input level Vrms Fig 36 Distortion on RECO versus input signal on RAUX Fig 37 shows the distortion of the signal on RECO as a function of the rms signal on RECO with a load of 5 and a line current of 15 mA 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 RECO output level Vrms Fig 37 Distortion on RECO versus level with 5 load 44 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 38 shows the noise on RECO loaded with 5 kQ psophometrically weighted P53 curve as a function of the line current This curve has been done with selection of the input IR which is left open With the antisidetone network connected to the input IR part of the microphone noise generated on the line will be added but thanks to the low microphone noise value the effect is almost negligible Noise dBVp 85 10 3 20 3 30 3 40 3 50 3 60 3 70 3 80 3 90 3 100 3 lline Fig 38 Noise on RECO 3 4 2 Earphone amplifier QR Principle of operation The earphone amplifier of the TEA1099 is able to drive loads down to an impedance of 150 As can be seen from fig 32 the earphone amplifier is an amplifier with the gain externally adjustable with a bridge
3. 000 E 0 20 E 3 40 E 3 60 E 3 80 E 3 100 E 3 120 E 3 140 E 3 160 E 3 180 E 3 lline 15mA lline 70mA lline 120mA Vdtmf Input level Vrms Fig 27 Distortion of the DTMF signal on line versus input signal 35 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 3 3 Handsfree microphone channel Principle of operation Fig 20 shows that the handsfree microphone channel is splitted into two blocks the handsfree microphone amplifier TXIN to TXOUT and the HFTX amplifier The handsfree microphone amplifier is referenced to pin GNDTX This is in order to prevent interference from other blocks of the TEA1099 or of the application GNDTX is called a clean ground The input and output signals of the microphone channel have to be referenced to GNDTX Pin GNDTX itself has to be shorted to GND The input of the handsfree microphone amplifier is pin TXIN It is an a symetrical input well suited for electret microphones Induced signals in the short wire between the microphone and pin TXIN are assumed to be negligible This is in contrary with the handset microphone which is connected via the handset cord The output of the microphone amplifier is pin TXOUT In handsfree mode pin TXOUT has to be connected via a decoupling capacitor to pin HFTX As can be seen in fig 20 between pins TXIN and TXOUT this microphone amplifier is built up out of two parts
4. 8 all r alls HE we glll al gl z 4 Fig 65 component placement diagram of the demoboard 87 Philips Semiconductors TEA1099 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer Application Note LNP Chal Rbal2 Rslpe Cz Rz 7 220 nF 118202 202 4 creg To 02 Rball a 4 7HF H Rage 1300 Rast3 0Q DG 9s 4p 3920 Rast2 16 18 py 100 HE Dz 3 92 SLPE REG AGC LN ZN Cir 17 ae nv I IR ae EXSI 100 nF 0 1N4004 Rast VBB VBB 130 kQ Cvbb T 470 pF 19 VDD VDD 13 Cvdd L GND T4 uF 29 GNDTX 44 AUXO tT AXO 20 1 Chrx 10 uF MES MICS HFRX 1 Cfeed 35 470 nF ene Rel T RECO tT L a 47nF 100kQ Cears GARX Ctx2 Coar InF 31 Re2 gar ibd p T 100 pF 33 uF 33 P Cear se TEA1099 QR 4 lt EARP Ctx 4 7 pF HMICM MIC 3 3 uF GALS Rgals Cgals 255 0 iss 43 LSAO LSOP TAXI TXAUX 220 uF 470 nF 23 Rvol Cmf 32 VOL N 1 DTMF 3 470
5. Fig 25 shows the common mode rejection ratio at 15 mA Two curves are present in this fig 25 the first one is the spectrum of the signal on pin LN when a microphone signal is applied on pin MIC while pin MIC is shorted to GND the second one is the spectrum of the signal on pin LN when a microphone signal is applied on pins 33 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer MIC and MIC shorted together Both signals are at 1 kHz the difference between the two curves gives the CMRR 11 29181246 0 500 1000 1500 2000 2500 3000 3500 4000 4500 mode handset Frequency Hz Fig 25 Common mode rejection ratio on microphone 3 3 2 DTMF amplifier Principle of operation The DTMF amplifier has an a symmetrical high input impedance of 20 between pins DTMF and GND with a maximum spread of 15 The input is biased at GND so if the input signal is polarized at GND there is no need of decoupling capacitor in series The DTMF amplifier is built up out of three parts an attenuator by a factor of 7 15 a preamplifier which realizes the voltage to current conversion and the same end amplifier as the handset microphone amplifier No AGC is applied to the DTMF channel The overall gain Giv dtmf In of the DTMF amplifier from input DTMF to output LN is given by the following equation Gv dtmf In
6. a aaa ae aaa aeaa 54 Fig 49 Typical behavior of the signal and noise detectors 55 Fig 50 Truth table of the decision logic 56 Fig 51 Behavior of the voice 57 Fig 52 Circuit for shifting the 61 Fig 53 GND and GNDTX connections ie nnns aaa e ea ataa E EEE ENTR 62 Fig 54 Table ofi connections oh Ete tete 65 Fig 55 Steps in the design flow of the TEA1099 ssssssssssssseeeeeeeerene nennen nennen snnt nnns 70 Fig 56 Basic handsiree application pendet e tiec eee ded ar eade Et Let their beares teu ei an inde tase 72 Fig 57 Group listenning conversation with antihowling ssssessseeenennnne nnns 73 Fig 58 Cordless conference with line base and 74 Fig 59 Cordless handsfree conversation in 75 Fig 60 Answering Machine on line E 76 Fig 61 Cordless intercom between mobile and base 5 77 Fig 62 Application with Fax Cordless and Answering 78 Fig 63 Typical external antihowling cirCuit sesenta 79 Fig 64 Schema
7. a preamplifier and an end amplifier The gain of the preamplifier is determined by the duplex controller block see 3 5 The gain of the end amplifier is determined by the external feedback resistor Rgatx The overall gain Gv txin txout of the microphone amplifier from input TXIN to output TXOUT in TX mode is given as Gv txin txout 20 log 0 7 Rgatx Rstab With Rstab being the resistor at pin STAB of 3 65 kQ The HFTX amplifier has an a symmetrical high input impedance of 20 between pins HFTX and GND with a maximum spread of 15 The HFTX amplifier is built up out of two parts a preamplifier which realizes the voltage to current conversion and the same end amplifier as the handset microphone amplifier The overall gain Gv hftx In of the HFTX amplifier from input HFTX to output LN is given by the following equation Gv hftx In 20 x log Avhft Avhft 1 93 x Rgasint Rrefint x Ri Zl Rslpe x with Ri the AC apparatus impedance Rcc Rp typically 620 25 Rgasint internal resistor realizing the current to voltage conversion typically 27 6 with a spread of 15 Rrefint internal resistor determining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgasint Zl load impedance of the line during the measurement gain control factor varying from 1 at lline 15 mA to 0 47 at 70 mA when AGC function
8. auxiliary inputs output and analog multiplexer Step Adjustment TEA1099 transmit gain in handsfree mode After the sensitivity and the curve of the microphone are adjusted the gain can be adjusted to the desired value Microphone sensitivity Rbmics sets the sensitivity and provides the polarisation of the electret Cmicb with Rbmics and the output impedance of the electret form a low pass filter Frequency curve Transmit gain and stability Ctxin with the 20 input impedance at TXIN form a high pass filter Rgatx sets the microphone amplifier gain Gv txin txout 20xlog 0 7 xRgatx Rstab The capacitor Catx in parallel with Rgatx forms a low pass filter The gain between HFTX and LN is fixed at 34 7 dB on 600 Chfx and HFTX input impedance form a high pass filter A resistor bridge attenuator may be inserted between TXOUT and HFTX or between Cixin and TXIN TEA1099 loudspeaker amplifier The gain is adjustable with Rgals a high pass filter can be made the dynamic limiter timing can be chosen Gain and frequency curve Rgals sets the loudspeaker amplifier gain Gvlsao 20xlog 0 35 xRgals Rstab Cgals forms a low pass filter with Rgals Chrx and or capacitor Clso in series with loudspeaker can form high pass filters Dynamic limiter timing Capacitor Cdlc at pin DLC TEA1099 receive channel The gain of the receive pass and the curve can be adjusted The volume control range can be chosen Receive gain The gain between IR
9. isis crei redacti bonae o ederet e e MR ct exu o ed rc ead d ER us 17 6 Ibb versus VOD iiie een ted rd edid nrc it eases ERR RSEN a aTa 18 7 Main voltages versus line current enne nennen nnne a ana e a ntis snnt nnns 18 8 Low voltage behavior in line powered nennen 19 9 Low voltage behavior when VBB 5 V eene nnn inneren inni nr nnnnr 19 10 Influence of the resistor between REG and SLPE on at 15 20 11 Influence of Rslpe on the DC 21 12 Equivalent set 21 13 Anti sidetone bridge connection ssssssssssssssssssssssseeenenne nennen hnnnnmen sse isset nnn 22 14 Equivalent average line impedance ssssssssssssssseeeeeeneneene nennen nennen nennen nnne nnn 23 15 AGC on the microphone gain versus line current and RagC 24 16 Block diagram of the supply block sssssssssssssssssseee eene nennen 25 17 Loudspeaker output power versus line nnne nnn 26 18 Current consumption on VBB in ring mode versus VBB ssssssss eene 28 19 Current consumption on
10. board User Manual 3 Philips Semiconductors SEMICONDUCTORS FOR WIRED TELECOM SYSTEMS IC03a Data handbook 4 Philips Semiconductors SEMICONDUCTORS FOR WIRED TELECOM SYSTEMS ICO3b Application handbook 81 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer APPENDIX LIST OF ABBREVIATIONS AND DEFINITIONS Aac Electro acoustic coupling electrically measured AGC Automatic line loss compensation of the TEA1099 Aloop Loop gain of a handsfree telephone set A M Answering machine Arx1099 Gain of the receive path of TEA1099 Ast Sidetone gain Asw Switching range Atsen Gain from TXIN to TSEN of 40dB Atx1099 Gain of the transmit path of TEA1099 AUXC Logic input AUXO Auxiliary amplifier output of TEA1099 BRL Balance Return Loss matching between the apparatus impedance and a reference Cgar Capacitor setting receive path amplifier low pass filter Catx Capacitor setting the base microphone amplifier low pass filter Cfeed Microphone supply filter capacitor Chrx Receive input capacitor Chfx Transmit output capacitor Clso Loudspeaker coupling capacitor Cmicb h Microphone low pass filter capacitors Crenv Capacitor determining the receive signal envelope Crnoi Capacitor determining the receive noise envelope Crsen DC blocking capacitor of receive sensitivity setting Cswt Switch over timing capacitor Ctenv Capacitor determining the transmit signal
11. dd 0 5 0 000 E 0 2 E 3 4 E 3 6 E 3 8 E 3 10 E 3 12 E 3 14 E 3 16 E 3 lline A Fig 8 Low voltage behavior in line powered condition Fig 9 shows the behavior in the low voltage area when VBB is externally supplied at 5 V 0 000 E 0 2 E 3 4 E 3 6 E 3 8 E 3 10 E 3 12 E 3 14 E 3 lline A Fig 9 Low voltage behavior when VBB 5 V 19 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Adjustments and performances The reference voltage Vref can be adjusted by means of an external resistor Rva It can be increased by connecting the Rva resistor between pins REG and SLPE Fig 10 or decreased by connecting the Rva resistor between pins REG and GND In line powered application it is possible to use the voltage reduction only for less than 300 mV because it reduces the VBB supply capability this reduction is easier when VBB is provided by an external 5 V power supply To ensure correct operation it is not advised to adjust Vref at a value lower than 3 3 V at 18 mA or higher than 7 V at a maximum line current of 90 mA the maximum operating voltage of 12 V must be guaranteed by the application as well as the safe crystal operating temperature These adjustments will slightly affect a few parameters there will be a small change in the temperature coefficient of Vref and a slight increase in the spread of this voltage r
12. when the voltage on SLPE is lower than VBB the line current is driven to GND when the voltage on SLPE is between VBB and VBB 0 3 V both transistors are conducting in order to minimize distortion The correlation between line voltage and line current is done in order to get the optimized correlation between the power that can be extracted from the line and the power that can be delivered to the loudspeaker amplifier Fig 7 shows these different voltages versus line current fig 17 shows the output voltage delivered on a 16 Q and on a 50 loudspeaker versus line current Level for 2 THD Vrms 1 8 0 8 0 6 0 4 0 2 0 015 0 025 0 035 0 045 0 055 0 065 0 075 Risan 50 7 77 Risao 16 lline A Fig 17 Loudspeaker output power versus line current The block diagram of Fig 16 shows that an external power supply can be connected at ESI the supply current detection block controls the selection of the supply used by sensing the current in a serial resistor When the current is flowing from SLPE to VBB line current is used as power source when current is flowing from ESI to VBB the external supply is then used and the shunt regulator built in the voltage stabilizer is adjusted to the external source clamping VBB at 6 6 V in order to get the value of VBB as close as possible to ESI value without extra current consumption This shunt regulator is switched off in power down mode only and
13. 1 6 V This means that more sets can operate in parallel or that for very low voltage feeding bridge the line current has a higher value For line currents below this threshold current the TEA1099 has reduced sending and receiving performances This is called the low voltage area The internal circuitry of the TEA1099 is supplied from pin VBB In line powered application this voltage is derived from the line voltage by the supply block and must be decoupled by a capacitor Cvbb Fig 6 shows 17 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer the IC current consumption Ibb as a function of the VBB supply voltage in handset mode and in handsfree mode handsfree mode _ handset mode 3 3 5 4 4 5 5 5 5 VBB V Fig 6 lbb versus Vbb Fig 7 shows the main voltages as a function of the line current in line powered conditions 000 E 0 20 E 3 40 E 3 60 E 3 80 E 3 100 E 3 120 E 3 140 E 3 lline A Fig 7 Main voltages versus line current 18 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 8 shows the behavior in the low voltage area in line powered condition V VLN 4 VSLPE 3 5 VBB 3 VDD 2 5 VMICS 2 1 5 1
14. 2 20 x log Avmf Avmf 0 66 x Rgasint Rrefint x Ri Zl Rslpe with Ri the AC apparatus impedance Rcc Rp typically 620 25 Rgasint internal resistor realizing the current to voltage conversion typically 27 6 kQ with a spread of 15 Rrefint internal resistor determining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgasint Zl load impedance of the line during the measurement Using these typical values in the equation and assuming Zline 600 we find a gain equal to Gv dtmf In 20 x log Avmf 25 4 dB 34 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 26 shows the frequency response of the DTMF amplifier at 15 mA and different temperatures gain dB 27 26 17 dB 26 B 25 88 dB 25 24 23 a ur 2f 21 20 10 100 1 000 10 000 gain259 75 gainm25 Frequency Hz Fig 26 DTMF gain versus frequency influence of the temperature The input of the DTMF amplifier can handle signals up to 180 mVrms with less than 2 THD Fig 27 shows the distortion on line versus the rms input signal at different line currents THD
15. Answering Machine outgoing RAUX gt RECO HFRX gt LSAO message DTMF gt LN CT gt RECO HF GL Tel Set DTMF dialling HFRX gt LSAO MICS QR TXAUX gt LN IR gt AUXO Answering machine incoming IR gt RECO HFRX gt LSAO message Fax with monitoring TXIN gt TXOUT HFTX gt AUXO Cordless intercom with base RAUX gt RECO HFRX gt LSAO A M record or listen with base TXIN gt TXOUT HFTX gt LN Handsfree conversation A M IR gt RECO IR gt AUXO record conv HFRX gt LSAO MICS MIC gt LN IR gt RECO Group listenning conversation IR gt AUXO HFRX gt LSAO A M record conv MIC gt TXOUT MICS QR Fig 54 Table of connections 65 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer In modes 1 and 10 the volume control doesn t operate In modes 11 12 13 14 and 17 the microphone channel of the duplex controller is muted and the receive mode is forced In mode 15 by connecting pin DLC to ground it is possible to force the duplex controller in transmit mode When VBB has not reached a value higher than 2 9 V or has fallen down below 2 5 V the logic inputs are ignored and the handset conversation mode is forced MIC gt LN IR gt RECO MICS QR are on 66 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 4 APPLICATION COOKB
16. For effective operation of the apparatus the TEA1099 must have a low resistance to the DC current and a high impedance to speech signals The Creg capacitor converted into an equivalent inductance see set impedance section realizes this impedance conversion from its DC value Rslpe to its AC value Zimp in the audio frequency range The DC voltage between pins LN and SLPE is proportional to the line current This general configuration is shown in fig 5 16 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Rline Iline management slope low voltage from transmit preamps Fig 5 DC characteristics configuration The IC regulates the line voltage between pins GND and SLPE The voltage on pin LN can be calculated as Vin Vref Rslpe Islpe Islpe lline IIn lline line current current consumption between LN and GND Between 18 and 46 mA Vref 3 7 Islpe 18 mA x 87 5 The DC line current Iline flowing into the apparatus is determined by the exchange supply voltage Vexch the feeding bridge resistance Rexch the DC resistance of the telephone line Rline and the voltage across the telephone set including diode bridge Below a threshold line current Ith typically equal to 9 mA the internal reference voltage generating Vref is automatically adjusted to a lower value down to an absolute minimum voltage of
17. TXOUT and the gain of the loudspeaker amplifier can be reduced by pulling pin DLC to GND The solution advised for this antihowling circuit is to measure the amplitude of the signal at pin TXOUT when it is too high for a too long time pull the pin DLC to GND This can be done with a very simple circuit where the time constants are set by capacitors see fig 63 Ringer mode In the ringer mode provided a switch mode power supply circuit DC DC converter has to be added to convert the input ringing signal into a DC supply connected at pin ESI The current coming from this supply is usually varying with the frequency of the input signal thus modulating the melody with this low frequency It is possible to reduce the acoustic effect of this modulation by slowing down the dynamic limiter This can be done by increasing the value of Cdlc in ringer mode from 0 47 uF to 10 uF switching a parallel 10 uF capacitor by means of a DMOS transistor 62 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 6 Logic block 3 6 1 Logic inputs In this chapter the 5 logic inputs which control the TEA1099 are described The selected channels for each combination of the logic inputs are depicted in fig 54 When a channel is selected the relevant preamplifier is switched on and all the others connected to the same end amplifier are switched off The end amplifiers the duplex controll
18. VDD at VBB 0 29 20 Block diagram of the transmit part ssssssssssssssssssssseee 30 21 Handset microphone gain versus frequency influence of temperature 32 22 Distortion on line versus handset microphone signal on 1099 32 23 Distortion of line signal at lline 4 33 24 Handset microphone noise versus line enne 33 25 Common mode rejection ratio on 34 26 DTMF gain versus frequency influence of the temperature 35 27 Distortion of the signal on line versus input signal sse 35 28 Connection of the handsfree electret microphone ssssssssssssssseeeeeee eene nnns 37 29 Distortion on line versus HFTX input 38 30 Distortion on line versus TXAUX input signal nennen nennen 39 31 Transmit noise versus line current ssssssssssessssssssssese eene nnn 39 32 Receive block diagram eene nnne 40 33 Block diagram related to AUXQO etit EE et erecta redes edad buda ger 41 34 Receive gain versus
19. biased at 2 Vd and can handle signals up to 580mVrms with less than 296 THD Fig 43 shows the distortion on AUXO when the limitation is related to the input voltage at HFRX for a line current equal to 75 mA 50 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer THD 25 0 0 1 02 03 04 05 06 07 08 HFRX Input level Vrms Fig 43 Distortion on AUXO versus input signal on HFRX The input HFTX is biased at 2 Vd and can handle signals up to 140 mVrms with less than 2 THD Fig 44 shows the distortion on AUXO for a line current equal to 75 mA 0 0 02 0 04 0 06 0 08 0 1 0 12 0 14 0 16 HFTX input level Vrms Fig 44 Distortion on AUXO versus input signal on HFTX Fig 45 shows the distortion of the signal on AUXO as a function of the rms signal on AUXO with a load of 5 kQ and a line current of 15 mA 51 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer THD 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 AUXO output level Vrms Fig 45 Distortion on AUXO versus level with 5 kO load Fig 46 shows the noise on AUXO loaded with 5 kQ psophometrically weighted P53 curve as a function of the line current This curve has been done with selection of t
20. block is fed from VBB and provides a 2 V regulated supply with a capability of 1 mA The output impedance is typically 200 Q and must be filtered with a capacitor referenced to GNDTX This output is switched off in power down mode and in modes where the electret microphones are not necessary see list in fig 4 Adjustments and performances When the output is filtered with a 10 capacitor to GNDTX the noise at MICS is typically 114 dBVp The value of this capacitor fixes the impedance of this supply point when the value of this capacitor is too small the attenuation of the handset microphone signal may not be sufficient compare to the switching range of the duplex controller 3 3 Transmit The selection of the signal transmitted on line is made according to the table of fig 4 This signal comes from the four following amplifiers handset microphone amplifier DTMF amplifier handsfree microphone channel and auxiliary transmit amplifier Fig 20 shows the block diagram of the transmit part 29 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer t Cexch Iline management slope low voltage Fig 20 Block diagram of the transmit part 30 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 3 1 Handset microphone amplifier Principle of operation The micropho
21. envelope Ctnoi Capacitor determining the transmit noise envelope Ctsen DC blocking capacitor of transmit sensitivity setting Ctxin Base microphone amplifier input capacitor dBmp dBm psophometrically weighted 0dBmp 1mW dBVp dBV psophometrically weighted OdBVp 1Vrms 82 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer DTMF Dual Tone Multi Frequency Vswt Voltage difference on SWT GALS Loudspeaker amplifier gain adjustment pin GARX Earphone amplifier gain adjustment pin GATX Base microphone gain adjustment pin GL Group listening GND Ground reference pin GNDTX Ground reference pin for microphone signals HF Handsfree HFC Logic input Handsfree on off HFRX Handsfree receive input HFTX Handsfree transmit input IDT Idle mode timing adjustment pin IR Receive input from line Istart Start current of the AGC function Istop Stop current of the AGC function Iswt Output current through pin SWT from decision logic Ix mode Idle mode k Scale factor of anti sidetone network Leq Artificial inductor of the voltage stabilizer LN Positive line terminal of TEA1099 LSAO Loudspeaker amplifier output of TEA1099 MIC MIC Microphone input of TEA1099 MICS Microphone supply of TEA1099 MOSFET Meta Oxide Field Effect Transistor MUTT Logic input MUTR Logic input PCB Printed circuit board PD Logic input power down input PTAT Proportional to absolute temperature PTT Public tele
22. in fig 48 is adjustable by Rrsen In a similar way as the coupling between the loudspeaker and the microphone is very strong a too high level of noise would be monitored at pin TNOI when dial tone is received This is prevented by clamping internally the level of noise that can be monitored on TNOI to a realistic value 0 75 mVrms at TXIN with Rtsen 10 When these three corrections are made the signal and noise envelopes are used by the comparators and the logic As already explained the output of the logic is a current source The relation between the current source and the output of the comparators is given in the table of fig 50 If for instance TENV gt RENV transmit signal larger than receive signal and TENV gt TNOI transmit signal more than 4 3 dB larger than noise level then the output current will be 10 pA Comparator TENV TNOI 1 X 0 X Comparator TENV RENV 1 0 0 1 0 Comparator RENV RNOI x 1 x x 0 Comparator RNOI Vat X X 1 X 0 Output current 100A 10 10 Fig 50 Truth table of the decision logic When pin DLC is forced to GND the output current is forced to be 10 uA which forces the TEA1099 into Tx mode and mutes the receive path The voltage on pin SWT is internally limited to IDT 0 4 V and IDT 0 4 V 3 5 3 Voice switch With the voltage on pin SWT the voice switch regulates the gain of the microphone preamplifier and the receive channel preamplifier in such a way that the sum of the transm
23. interface part of the TEA1099 circuit by means of a receiving preamplifier a transmit amplifier and the hybrid The right side of fig 1 shows a principle diagram of the handsfree part of the TEA1099 circuit by means of the microphone preamplifier the loudspeaker amplifier and the duplex controller As can be seen from fig 1 a closed loop is formed via the amplifiers the antisidetone network and the acoustic coupling between loudspeaker and microphone When the loop gain is higher than one the set starts Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer howling In a full duplex application this would be the case To avoid howling the duplex controller reduces the loop gain to a value much lower than one The duplex controller of the TEA1099 monitors the signal and noise on both the transmit and the receive channel in order to detect which channel contains the largest signal As a result the duplex controller reduces the gain of the channel which contains the smallest signal The sum of the transmit and the receive gains remains constant As a result the circuit can be in three stable modes to be referred to throughout this report 1 Transmit mode Tx mode the gain of the handsfree microphone path is at its maximum the gain of the receive path to loudspeaker amplifier is reduced 2 Receive mode Rx mode the gain of the receive path is a
24. is applied see chapter 3 1 4 for details Using these typical values in the equation and assuming Zline 600 Q we find a gain equal to Gv hftx In 20 x log Avhft 34 7 dB at lline 15 mA 36 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Adjustments and performances A handsfree microphone referenced to GNDTX can be connected to the input TXIN via a DC blocking capacitor Ctxi Together with the input impedance at pin TXIN of 20 kQ this capacitor form a first order high pass filter which can be used to adjust the transmit curve The handsfree electret microphone can be supplied from MICS via a resistor MICS TXIN GNDTX Fig 28 Connection of the handsfree electret microphone The sensitivity of the electret microphone is set via resistor Rmic By putting a capacitor Cmic in parallel with the microphone a first order low pass filter is formed for the microphone signal in order to adjust the transmit curve Via the resistor Rgatx the gain of the microphone amplifier can be adjusted from 6 to 31 dB to suit application specific requirements With the resistor Rgatx 30 kQ the gain equals typically 15 dB Capacitor Cgatx can be applied in parallel with resistor Rgatx to provide a first order low pass filter for the adjustment of the transmit curve The input of the microphone amplifier can handle signals up to 18 mVrms with 2 total ha
25. is still available in ringer mode A low VBB condition detection block detects if the value of VBB becomes higher than 2 9 V The logic block is enabled when VBB becomes higher than 2 9 V The handsfree and the loudspeaker amplifier parts are enabled when VBB becomes higher than 2 9 V 26 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer When VBB becomes lower than 2 7 V the VBB detector of the dynamic limiter on LSAO discharges the capacitor at pin DLC and the loudspeaker amplifier is disabled This block detects also if VBB becomes lower than 2 5 V When VBB becomes lower than 2 5 V the logic block is disabled and the handset speech mode is forced Moreover the handsfree and the loudspeaker amplifier are disabled The difference between 2 5 V and 2 9 V make hysteresis in order to keep stable behaviors VBB can be used to supply external circuits in line powered condition the total amount of current drawn from VBB MICS and from VDD must be low enough to stay compatible with the value of the line current A starter block is included in order to speed up the charge of the capacitor Cvbb This starter is active as soon as some voltage is available on the line when VBB is still lower than 2 4 V when VBB is decreasing it becomes active again when VBB becomes lower than 1 9 V Adjustments and performances A capacitor Cvbb must be connected betwee
26. mV which is equal to 7 6 dB at room temperature The new speech noise threshold is slightly dependent on temperature and on the spread of the internal current source and therefore less accurate than the internal 4 3 dB It is advised not to use a resistor larger than 12 61 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Ground layout The layout of the ground is very important for noise and for the duplex controller behavior In fact high currents generate residual voltages on the PCB and these voltages may affect dramatically some references or may couple loudspeaker signal with microphone Fig 53 gives a reference for the connection of different components to the grounds LSAO TEA1099 Rstab Cfeed Cswt Rvol Rswr GNDTX GND Et 1 1 d ox c Crsen Ctsen Crenv Ctenv Crnoi Ctnoi Fig 53 GND and GNDTX connections Antihowling In group listening application there is an acoustic coupling between the loudspeaker and the handset microphone When the microphone is too close to the loudspeaker the gain of the loop becomes higher than 1 and howling occurs This howling may disturb the other party specially if it is an operator with a headset Around the TEA1099 it is possible to build an antihowling circuit which limits this howling For this purpose in group listening mode the microphone signal is amplified by 49 8 dB at pin
27. means that at nominal receiving signal the current through RSEN is preferably around 11 This gives a maximum dynamic range of plus and minus 23 The same counts for pin TSEN The resistor Rtsen has to be preferably chosen in such a way that both channels have the same priority for the duplex controller This can be obtained by choosing Rtsen according to 20 log Rtsen 20 log Rrsen Atx1099 Ast Arx1099 Atsen 1 2 Aloop with Atsen internal gain from TXIN to TSEN 40 In this formula the maximum loop gain and the worst case sidetone are used If it is preferred to give the transmit channel priority above the receive channel the value of Rtsen has to be chosen smaller For the opposite the value of Rtsen has to be chosen larger With respect to the calculated setting Rtsen and Rrsen can be varied with plus and minus 1 2 Aloop in dB The capacitors Ctsen and Crsen form first order high pass filters respectively with Rtsen and Rrsen to reduce influence of low frequencies on the switching behavior It is suggested to choose the capacitors Ctsen and Crsen such that the cut off frequencies of the filters are similar When the calculated sensitivity setting is implemented subjective tests with real telephone lines will be necessary to come to the optimal sensitivity setting Once Rrsen is determined it would also be possible to determine Rtsen only by experiments In this case subjective tests with
28. the Ix mode is set by the combination Cswt and Ridt The switching range is determined by the resistor Rswr Resistor Rstab has a fixed value Logic block The logic block manages the internal switches according to the following table 14 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer __ LOGICINPUTS CONNECTIONS MODES MES NN NE 2 penasso Nm _ ee eee Ee si DC EA mode m DTMF gt LN CT gt RECO Tel Set dialling MICS QR MIC gt AUXO RAUX gt RECO MIC gt AUXO RAUX gt RECO Bi 1 X MIC gt LN IR gt RECO IR gt AUXO Handset conversation MIC gt TXOUT MICS QR eorars rae TXAUX gt LN IR gt AUXO Conversation with auxiliary TXAUX gt LN IR gt AUXO RAUX gt RECO TXIN gt TXOUT HFTX gt LN ee les EX HFRX gt AUXO 1 RAUX RECO HFRXLSAO gt HFRX gt LSAO TXAUX gt LN IR AUXO RAUX gt RECO HFRX gt LSAO DTMF gt LN CT gt RECO HF GL Tel Set DTMF HFRX gt LSAO MICS QR dialling TXAUX gt LN IR 2AUXO IR RECO HFRX gt LSAO TXIN gt TXOUT HFTX gt AUXO RAUX RECO HFRX gt LSAO MICS TXIN gt TXOUT HFTX gt LN Handsfree conversation IR RECO IR gt AUXO HFRX gt LSAO MICS MIC gt LN IR gt RECO Group listenning IR gt AUXO HFRX gt LSAO conversation MIC gt TXOUT MICS QR Fig 4 Table of switch management 15 Philips Se
29. the gains of the controlled amplifiers are also reduced When the line current reaches an other threshold current Istop typically 57 mA the gain control factor is limited to its minimum value equal to 0 49 or 0 47 giving the lower value to the transmit and receive controlled gains The gain control range of these amplifiers is typically 6 2 dB or 6 6 dB depending on the amplifier see datasheet which corresponds approximately to a line length of 5 5 km 0 5 mm twisted pair copper with an attenuation of 1 2 dB km The attenuation is correlated to the current lagc sunk at pin AGC when this current is lower than typically 4 8 the gains are maximum when this current is higher than typically 12 A the gains are minimum This current is proportional to the voltage between pins SLPE and LN There is an internal resistor which sets Istart and Istop adding Ragc externally in series between pins AGC and LN reduces lagc and increases the values of Istart and Istop 23 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Adjustments and performances The AGC of the TEA1099 can be used with different exchange supply voltages and different feeding bridge resistances For this purpose a resistor Ragc can be inserted between pins AGC and LN This Ragc resistor increases the two threshold currents Istart and Istop Fig 15 shows the control of the microphone gain versus th
30. varies no current will flow from VDD to VBB via this pin The threshold voltage level is 0 65 V typically with a temperature coefficient of 2 mV C The input voltage must stay within the limits GND 0 4 V to VBB 0 4 V Input MUTR This input is active low it must be driven by a push pull structure the threshold voltage level is 0 65 V typically with a temperature coefficient of 2 mV C The input voltage must stay within the limits GND 0 4 V to VBB 0 4 V When using a standard dialler for only basic applications handset mode handsfree mode and dialling modes this input has to be connected to MUTT input In this configuration when MUTT MUTR are low the TEA1099 is switched to DTMF dialling mode Input HFC This input is active high it can be driven by an open drain structure because the pull down is included the threshold voltage level is 1 3 V typically with a temperature coefficient of 4 mV C The input voltage must stay within the limits GND 0 4 V to VBB 0 4 V When active the input HFC switches on the duplex controller block if the supply condition enables it see 53 2 1 63 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer If the supply conditions are such that the handset conversation mode is forced this pin becomes an output at logic level 0 with an output sink capability of 300 pA Input AUXC This input is active
31. will be 8 5 dB ms l 120 YA This is enough to track the signal envelope during release because the signal envelope release timing is 0 7 dB ms which is a factor smaller It is advised to choose the signal envelope timing and the noise envelope timing of both channels equal for optimum operation of the duplex controller The switch over timing is determined by the value of the switch over capacitor Cswt The idling timing is determined by the combination of Cswt and the idling resistor Ridt The output current of pin SWT is Iswt a voltage difference over Cswt can be obtained according to dVswt t Iswt Cswt mV ms With the advised value of 220 nF for Cswt the obtained voltage difference is 45 mV ms The switch over time is dependent on the voltage difference which has to be generated on pin SWT Assuming the set is in full Tx mode then the voltage on SWT will be V IDT 400 mV see fig 51 To reach Rx mode a voltage difference of 580 mV must be generated to end up a voltage of V IDT 180 mV So in this case the switch over time will be 13 ms When the set is in Ix mode the voltage on SWT equals the voltage on IDT in that case switching to Tx mode or to Rx mode requires a voltage generation of only 180 mV and they will be reached in 4ms The idling timing is determined by an RC time constant It is supposed that Ix mode is reached when a time tidt is elapsed tidt 4 Ridt Cswt With the advised value for Ridt of 2 2 MO an idli
32. APPLICATION NOTE Application of the TEA1099 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer AN98061 PHILIPS PHILIPS Semiconductors Philips Semiconductors TEA1099 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer Application Note Abstract The TEA1099 is a bipolar circuit which includes line interface speakerphone function and switches for connection of auxiliary interfaces lt is intended to be used in line or mains powered telephone terminals A detailed description of the circuit blocks of the TEA1099 and advices on adjustments are contained in this report Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer APPLICATION NOTE Application of the TEA1099 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer AN98061 Authors D Delbecq A Gauthier J M Malaurie Business Line Communication Caen France Keywords Telecom Demonstration Board TEA1099 transmit receive auxiliary line Date June 11th 1998 3 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Summary A detailed description of the TEA1099 is given The TEA1099 incorporates a line interface block with microphone earphone and DTMF amplifiers It incorporates also a duplex controller with signal an
33. DECISION lOG Crisan a A ae ae 55 3 53 VOICE SWIT Mera Ee 56 3 5 4 Adjustments and performances of the duplex 57 SERM CLIE 63 3 53I Eogic Inplits sx tbe fun ep foe doo cec on cuoc 63 3 672 CONNECTIONS aer tte teret er tec ire ira ENT ea 64 4 APPLICATION COOKBOOK 5 1 22 20 21 2 2 piae cap natio 67 5 Adae wie i241 dace ERG 71 6 ELECTROMAGNETIC COMPATIBILITY 80 T RBEFERENGES eei 81 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer LIST OF FIGURES Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig Fig 1 Handsfree telephone Set 8 2 Block diagramof TEATOO9 5t et eure db ran E bebe pier fcc eu e 10 3 Pinning otTEATOO99 eee ith et cee etek ttti eue 11 4 Table of switch 15 5 DG characteristics configuration
34. EA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer DLC Fig 63 Typical external antihowling circuit 79 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 6 ELECTROMAGNETIC COMPATIBILITY As no common international specification exists for immunity and as different assembly methods may lead to different solutions only some advices can be provided It is advisable to take care of the impedance of the GND the smallest is always the best Even if it is required to separate low level microphone signals on GNDTX from high level signals loudspeaker or others GND and GNDTX traces must be as wide as possible Also the connection of Rstab Rswr Rgatx Rgals and Rgarx has to be done with very short traces specially STAB input which sets all the gains must be very immune VOL MIC MIC HFTX TXAUX and TXIN inputs may also be sensitive RF signals entering these pins would be amplified Rvol must preferably be connected with short traces or VOL input may be lightly decoupled by a capacitor to GND or better the trace must be inserted between GND traces Care has to be taken with the lay out of the microphone amplifiers which is also helpfull for the noise providing a good decoupling to GNDTX Low pass RC filters may be added at the inputs of the amplifiers C3 C4 C8 on the demoboard The output TX
35. ED 2 i 150 pF 26 P E J 48 20 kQ up Rbmics SH Rid 470 1020 2kQ LR 47 kQ Ru ON IM a A OG 87 ANTIHOWLING CIRCUITRY 1 TXIN Abe N EE pute rede Dco Susa dicen Cmicb 15nF 00 Rbm2 4 Rtsen Ctsen O T22nF S R 100 pF IO kQ 100 nF BMICM E 3 ev 740 TT RAXI tf RAUX 047 uF 100 nF 38 2 Rtnoi Ctnoi PD e Es PD TNOI ra due HFC un Rmoi 39 MUTT 00 4 7 uF MUTT 20 1 MUTR MUTR RENV 41 AUXC gt AUXC 6 Rrsen Crsen Rstab 21 10kQ 100 nF STAB Cowt 3 65 SwpE Rswr 22 Ridt 220 nF SWR IDT SWT 365 22 IDT Fig 64 Schematic of the demoboard 86 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer HFC PD HUTT MUTR AUXC fal A AXO T C C C DEMOBOARD FOR TER1099 nem tus sl cTNOI R CEAR i 41 E Es g g 5 z n e 015846 3 T rud SWT ce CRENV E IDT cez RVOL B LNP C VBB Li oOo cy m amp 8 1 GND 8 cate cLso Ei CFEED VDD C20 L Ie en Tcl il e cn il us E BHICH 8 STi gl Ex got 5 8 8 IS alll 8181 95 BI ul 7 amp So E at 4j a all Sat 5 zw ll L a 3 al HIE a Ell 81 Bg al T 118
36. FACE s DUPLEX CONTROLLER GAIN CONTROL DLC pec UE M leas Fig 2 Block diagram of TEA1099 10 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Ze CoD KYL E KaD EE ees 8 lt E 43 gt Z HFRX EH QR TNOI 2 DTMF MIC TSEN 4 RNOI 5 GNDTX RSEN 6 1099 TXIN RENV Ej7 GATX DLC ws TXOUT ESI wo IDT VBB zo SWT GALS Egi VOL N 15 16 17 LSAO GND SLPE LN REG IR AGC VDD MICS STAB SWR Fig 3 Pinning of TEA1099 DESCRIPTION Receive input for loudspeaker amplifier or auxiliary receive amplifier Transmit noise envelope timina adiustment Transmit sianal envelope timina adiustment Transmit siqnal envelope sensitivity adjustment Receive noise envelope timina adiustment Receive siqnal envelope sensitivity adiustment Receive siqnal envelope timina adiustment OOA WP Dynamic limiter External supply input Stabilized supply for internal circuitry Loudspeaker amplifier qain adiustment Loudspeaker amplifier output Ground reference Line current sense 11 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Positive line terminal Line voltage requlator decoupling Receive channel input Automatic gain control 3 35 V supply v
37. OOK In this chapter the procedure for making a line powered handsfree handset basic application with the TEA1099 is given With the help of fig 64 in appendix the design flow is given as a number of steps which should be made As far as possible for every step the components involved and their influence on every step are given Fig 64 is the schematic of the OM5846 demoboard so the values of the components are proposed but the adaptation to the application can be done by modifying these values 67 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Step Adjustment DC setting Adjust the DC setting of the TEA1099 to the local PTT requirements Voltage LN GND This voltage can be adjusted by increasing Vref up to 7 V at max line current with the Rva resistor between pins REG and SLPE DC slope Not advised to modify Supply point VBB Optimize the value of Cvbb Supply point VDD Optimize the value of Cvdd Artificial inductor Its value can be adjusted by changing the value of Creg a smaller value speeds up the DC current shape during transients but decreases the value of the inductance and therefore affects the BRL at low frequencies Impedance sidetone and AGC After setting the required set impedance the sidetone has to be optimized using the sidetone network in order to minimize the loop gain in all line conditions AGC can be adjusted at that ste
38. OUT may also be sensitive to high interference it can be decoupled to GNDTX with a small capacitor lt 56pF Ctxor on the demoboard It can be helpfull to decouple the receive input IR two possibilities are offered a capacitor smaller than 220 pF between IR and GND C10 on the demoboard or a capacitor lower than 2 2 nF between IR and LN C21 on the demoboard It is not allowed to put a capacitor directly between STAB and GND only an RC network could be implemented if it helps 365 O 4 7 nF Low impedance capacitors in parallel with the electrolythic one between VBB and GND may help Usually a low impedance capacitor connected between LN and GND helps for the conducted interferences but this capacitor is in parallel with the impedance network of the apparatus so its value must be small enough In general when connections are coming from external environment e g MIC MIC A B on the demoboard it is better to filter the RFI signal before it influences the close environment of the TEA1099 e g action of C1 C2 C6 C11 which are close to the connectors on the demoboard 80 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 7 REFERENCES 1 TEA1099 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer Device specification 2 OM5846 Speech and Handsfree IC with auxiliary inputs output and analog multiplexer Demonstration
39. ain 25 Frequency Hz Fig 214 Handset microphone gain versus frequency influence of temperature Fig 22 shows the distortion of the signal on the line as a function of the microphone signal at nominal DC settings and for a different line currents THD 2 0 8 0 6 1 0 4 0 2 cM EI I ee ee p 0 000 E 0 1 E 3 2 E 3 3 E 3 4 E 3 5 E 3 6 E 3 7 E 3 8 E 3 9 E 3 10 E 3 lline 15mA lline 70mA _____lline 120mA Vmic Input level Vrms Fig 22 Distortion on line versus handset microphone signal on TEA1099 32 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 23 shows the distortion of the line signal versus level at line current of 4 mA THD 2 9 000 E 0 20 E 3 40 E 3 60 E 3 80 E 3 100 E 3 120 E 3 140 E 3 160 E 3 180 E 3 200 E 3 VLN Output level Vrms Fig 23 Distortion of line signal at lline 4 mA Fig 24 shows the microphone noise psophometrically weighted P53 curve versus line current when a 200 Q resistor is connected between the inputs MIC and MIC Noise dBmp 70 71 72 73 74 75 76 77 78 79 80 15 E 3 25 E 3 35 E 3 45 E 3 55 E 3 65 E 3 75 E 3 lline A Fig 24 Handset microphone noise versus line current
40. ain Gv mic auxo of the auxiliary handset microphone amplifier from input MIC MIC to output AUXO is given by the equation Gv mic auxo 20 x log Avhmax Avhmax 2 78 x Rgara Rrefint This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gv mic auxo 20 x log Avhmax 25 2dB Adjustments and performances 32 8 dB of receive gain between IR and AUXO compensate approximately the attenuation provided by the antisidetone network Fig 41 shows the frequency response of the auxiliary receive amplifier from IR to AUXO at different temperatures 49 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer GAIN dB 33 5 33 31 dB i 327708 i GAIN254 GAIN75 GAIN 253 Frequency H2 Fig 41 Auxiliary receive gain versus frequency influence of temperature The output is biased at 2 Vd with a temperature drift of 4 mV C so the maximum output swing on AUXO depends hardly on the value of VBB The receiving input IR can handle signals up to 50 mVrms with less than 296 THD Fig 42 shows the distortion on AUXO for a line current equal to 75 mA 0 5 10 15 20 25 30 35 40 45 IR input level mVrms Fig 42 Distortion on AUXO versus input signal on IR The input HFRX is
41. al to Gv ir auxo 20 x log Avrax 32 8 dB at lline 15 mA HFRX has an a symmetrical high input impedance between pins HFRX and GND shared with the HFRX to LSAO amplifier It is equal to 20 kQ with a maximum tolerance of 15 and the input is biased at 2 Vd The gain of the preamplifier is determined by the duplex controller block The overall max gain Gv hfrx auxo of the auxiliary amplifier from input HFRX to output AUXO is given by the equation Gv hfrx auxo 20 log Avreax Avreax 0 233 x Rgara Rrefint This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gv hfrx auxo 20 x log Avreax 3 7 dB HFTX has an a symmetrical high input impedance between pins HFTX and GND shared with the HFTX to LN amplifier It is equal to 20 with a maximum tolerance of 15 and the input is biased at 2 Vd The overall gain Gv hftx auxo of the auxiliary amplifier from input HFTX to output AUXO is given by the equation Gv hftx auxo 20 x log Avbmax Avbmax 0 88 x Rgara Rrefint This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gv hftx auxo 20 x log 15 2 dB MIC MIC has symmetrical high input impedances typically 70 2 times 35 kQ between pins MIC and MIC with maximum tolerances of 15 shared with the MIC MIC to LN amplifier It is equal to 20 with a maximum tolerance of 15 The overall g
42. alue The voltage on IDT is approximately 1 2 V so with for instance Rdiv1 33 kQ and Rdiv2 1 MQ the shift will be about 10 dB It is advised not to choose Rdiv2 lower than 1Mohms in order to limit the current drawn from IDT By connecting Rdiv2 to VBB instead of GND the idle mode is shifted towards the receive mode Signal to Noise ratio In noisy environments like offices a handsfree set can show an unsteady behavior in idle mode unwanted switching over from Ix to Tx mode In the TEA1099 this unsteady behavior is reduced by the implemented speech noise threshold of 4 3 dB However when a larger threshold is required this can be achieved by connecting a resistor Rtnoi in series with Ctnoi When there is only noise present at the input of the envelope detector the voltages on pins TENV and TNOI are equal When suddenly a signal is present the level on TENV will increase Without Rtnoi the voltage on TNOI will increase only slowly because of the charging current of 1 uA When a resistor Rtnoi is placed in series with Ctnoi under the same conditions this 1 current will cause a voltage jump on TNOI This jump determines the shift of the speech noise threshold As explained in 83 5 2 at room temperature the 4 3 dB threshold equals 13 mV A resistor Rtnoi in series with Ctnoi will add an extra voltage to this threshold of 1 pA x Rtnoi When for instance a resistor of 10 is chosen for Rtnoi the speech noise is increased to 23
43. and RECO is 29 7 dB which compensate the sidetone attenuation minus 2 3 dB Receive curve A bridge attenuator may be inserted between RECO and HFRX Chrx_with the input impedance of 20 kQ at pin HFRX form a high pass filter a cut off frequency between 100 and 200 Hz is advised Volume control A linear potentiometer of 22 kO is suggested 3 dB for each 1 9 kQ 69 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Step Adjustment TEA1099 Duplex controller see 3 5 When all gains are adjusted the switching range can be determined Then the dial tone detector level followed by the sensitivities can be set Finally the timings of the envelopes and the switching are adjusted Switching range Loop gain Aloop Atx1099 Ast Arx1099 Aac Asw lt 0dB Choose Asw with safety margin Adjust Rswr Asw 20log Rswr Rstab with Rstab fixed at 3 65kQ Dial tone detector Rrsen Vdialtone 2 5 uAxRsen Sensitivities Rtsen for balanced sensitivities between Tx and Rx Ctsen form a high pass filter with Rtsen Crsen form a high pass filter with Rrsen Signal envelopes Ctenv 0 47 uF Crenv 0 47 pF maximum attack 140 u 3xCenv dB ms release 1 dB ms Noise envelopes Ctnoi 4 7 pF 4 7 attack 1 u 3xCtnoi dB ms maximum release 140 u 3xCtnoi dB ms Switch over timing Cswt 220 nF 5Vswt t 10u Cswt mV ms Ix mode ti
44. between RECO GARX and QR The output is a rail to rail structure suitable for several kind of earpieces and can drive either dynamic magnetic or piezo electric earpieces In case of magnetic or dynamic earpieces a capacitor in series is required for decoupling in case of pure capacitive load a resistor in series is required for stability Adjustments and performances It is possible with a capacitor in series between RECO and GARX to built a high pass filter and with the capacitor Cgar in parallel with Rgarx to built a low pass filter To ensure stability a capacitor Cgars Cgars 10 x Cgar between pins GARX and GND is necessary The output is biased at 2Vd with a temperature drift of 4 mV C so the value of VBB affects hardly the output swing capability When the output is not enabled there is still an AC path through the gain resistors its attenuation depends on the value of these resistors a value of 100 min is advised for Rgarx Fig 39 shows the distortion on QR versus level at lline 15 mA on 150 Q and 470 Q loads in line powered conditions 45 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 1 1500hm 4700hm Output level Vrms Fig 39 Distortion on QR versus level 3 4 3 Loudspeaker amplifier LSAO Principle of operation As can be see
45. by experiments As for the calculation it is necessary to identify what the worst conditions are for sidetone and acoustic coupling In these worst conditions Rswr can be adjusted in such a way that the handsfree telephone set is at the limit of howling Then the determined value of Rswr must be increased in order to have a margin of 8 dB to 15 dB Handsfree behavior will be more comfortable for the user if the switching range is not too large So it is advised to take care of the acoustic coupling between the loudspeaker and the microphone which might come from the cabinet of the terminal itself Ad 2 Determine dial tone detector level The dial tone detector level on HFRX is determined by the value of Rrsen according to 58 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Vdialtone 2 5 Rrsen With Rrsen of 10 kQ the dial tone detector level will be 25 mVrms This means a continuous signal on the input HFRX larger than 25 mVrms will be recognized as a dial tone Ad 3 Determine sensitivity The sensitivity is set by Rrsen and Rtsen The resistor Rrsen is already determined by the dial tone detector level It must however be checked if the chosen value for Rrsen is a practical one for the dynamic range of the logarithmic compressor The optimized range for the compression is when the current flowing through pin RSEN is between 0 8 to 160 Arms This
46. by the second stage to pin TENV As the buffer can source 120A and sink 1A the signal on follows the positive peaks of the compressed signal this signal is called the signal envelope The time constants of the signal envelope are therefore determined by the combination of the internal current sources and the capacitor Ctenv The voltage on is buffered by the third stage to pin TNOI As this buffer can source 1 uA and sink 120 the signal on TNOI follows the negative peaks of the signal on TENV This is called the noise envelope because it represents the background noise The time constants of the noise envelope are determined by the combination of the internal current sources and the capacitor Ctnoi Both capacitors Ctnoi and Crnoi are provided with a start up circuit During start up the capacitors are charged with approximately 40 pA up to 1 9 V The starter will restart when the voltage on the capacitors drops below 0 9 V As can be seen in fig 48 the principle of operation of the signal and noise envelope detectors of the receive channel is equal to the one of the transmit channel However the gain of the first stage input to pin RSEN is 0 dB instead of 40 dB for the transmit channel this is in order to compensate the level on TXIN which is not yet amplified The behavior of the envelopes is illustrated in fig 49 where the signal and noise envelope of one channel are depicted together with the input signal V N
47. compensate approximately the attenuation provided by the antisidetone network minus 2 dB Fig 34 shows the frequency response of the line receive amplifier from IR to RECO at different temperatures 42 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer IGAIN dB 30 02dB 100 1 000 10 000 GAIN251 GAIN754 2 GAIN 254 Frequency Hz Fig 34 Receive gain versus frequency influence of temperature The output is biased at 2 Vd with a temperature drift of 4 mV C so the maximum output swing on RECO depends hardly on the value of VBB The receive input IR can handle signals up to 50 mVrms with less than 296 THD Fig 35 shows the distortion on RECO when the limitation is related to the input voltage at IR for a line current equal to 70 mA THD 25 0 10 20 30 40 50 60 70 VIR input level mVrms Fig 35 Distortion on RECO versus input signal on IR 43 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer The receive input RAUX is biased at 2 Vd and can handle signals up to 900 mVrms with less than 2 THD Fig 36 shows the distortion on RECO when the limitation is related to the input voltage at RAUX for a line current equal to 15 mA
48. d a gain equal to Gv txaux In 20 x log Avtxa 12 6 dB at lline 15 mA The input of the TXAUX auxiliary amplifier is biased at two Vd and can handle signals up to 1 Vrms with less than 2 THD and signals up to 50 mVrms with less than 0 1 THD Fig 30 shows the distortion on line versus the rms input signal at lline 70 mA 0 0 2 0 4 0 6 0 8 1 1 2 1 4 TAUX Input level Vrms Fig 30 Distortion on line versus TXAUX input signal Fig 31 shows the transmit noise psophometrically weighted P53 curve versus line current when a 2 kQ resistor is connected between the inputs TXAUX and GND Noise dBmp 75 85 000 E 0 10 E 3 20 E 3 30 E 3 40 E 3 50 E 3 60 E 3 70 E 3 lline A Fig 31 Transmit noise versus line current 39 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 4 Receive The receive part includes four different amplifier outputs line receive amplifier RECO earphone amplifier QR loudspeaker amplifier LSAO auxiliary receive amplifier AUXO and two different inputs IR from line and RAUX from auxiliary The selection of the receive signal is made according to the table of fig 4 Fig 32 shows the block diagram of the receive part while fig 33 shows the block diagram related to the auxiliary output AUXO DTMF HFRX IR udi Bite Fi
49. d noise monitors on the transmit and receive channels a base microphone amplifier as well as a loudspeaker amplifier In addition two auxiliary inputs and one auxiliary output combined with integrated switches allow the use of the TEA1099 in a lot of applications which can be either line powered or powered from the mains A cookbook gives the general application steps A demonstration board OM5846 is available Note The information presented in this document does not form part of any quotation or contract is believed to be accurate and reliable and may be changed without notice No liability will be accepted by the publisher for any consequence of its use Publication thereof does not convey nor imply any licence under patent or other industrial or intellectual property rights Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer CONTENTS T INTRODU CTO N a c 8 2 BLOCK DIAGRAM A a aa Sia 10 3 DESCRIPTION OF THE TEATO99 11er eere 16 3 1 Eineinterla Cenin 16 3 11 DG CharacteriStiGs 16 3 T1 2 EineampedariCe oie 21 3 1 3 Anti sidetone network eee daeee iss
50. d way for the design of the anti sidetone network as shown in fig 13 GND RECO AUXO Fig 13 Anti sidetone bridge connection This anti sidetone bridge has the advantage of a relative flat transfer function in the audio frequency range between the line and the outputs RECO or AUXO both with real and complex set impedances Furthermore the attenuation of the bridge for the receive signal between pins LN and IR is independent of the value chosen for Zbal after the set impedance has been fixed and the condition shown in equation st is fulfilled Therefore readjustment of the overall receive gain is not necessary in many cases The anti sidetone circuit is composed of Rcc Zline Rast1 Rast2 Rast3 Rslpe and Zbal Maximum compensation is obtained when the following conditions are fulfilled Rslpe x Rast1 Rec x Rast2 Rasts st k Rast2 x Rast3 Rslpe Rasti x Rslpe Zbal Zline The scale factor k is chosen to meet the compatibility with a standard value of capacitor for Zbal 22 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer In practice Zline varies strongly with line lenght and line type Consequently the value for Zbal has to be chosen to fit with an average line length giving acceptable sidetone suppression with short and long lines The suppression further depends on the accuracy with which Zbal equals this average l
51. different line conditions attenuation impedance length have to be carried out until the optimal sensitivity setting is found Ad 4 Determine timings The timings which can be set are signal envelope timing and noise envelope timing for both channels switch over timing and idling timing The signal envelope timing is set by the capacitors Ctenv and Crenv Because of the logarithmic compression between TSEN and respectively RSEN and RENV the timing can be expressed in dB ms At room temperature the following relation counts Timing 3 C dB ms With I charge or discharge current from pin RENV TNOI RNOI C timing capacitor Ctenv Crenv Ctnoi Crnoi With the advisable signal envelope timing capacitors Ctenv and Crenv of 470 nF the maximum attack timing of the signal envelopes will be around 85 dB ms 12120 pA This is enough to track normal speech The release timing will be 0 7 dB ms 1 1 pA This is enough to smoothen the signal envelope and to eliminate the influence of room echoes on the switching behavior 59 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer With the advisable noise envelope timing capacitors Ctnoi and Crnoi of 4 7 uF the attack timing of the noise envelopes will be 0 07 dB ms 1 1 pA This is small enough to track background noise and not to be influenced by speech bursts The maximum release timing
52. e line current for two values of Ragc When no AGC function is required the AGC pin must be left open then the control factor a equals to 1 and both controlled gains are at their maximum values When Ragc 0 and the value of Istart is too high increasing slightly the value of Rslpe reduces proportionally Istart and shifts the AGC to lower currents but the gains the DC characteristic and the value of VBB are also modified If the value of Rslpe has to be increased it is possible to restore the typical gains but not the value of VBB by connecting in parallel an RC series network which makes a total AC impedance of 20 O mic to In dB 45 44 43 42 41 Ragc ext 0 81 40 39 BEN 38 0 015 0 02 0 025 0 03 0 035 0 04 0 045 0 05 0 055 0 06 0 065 0 07 0 075 0 08 0 085 0 09 0 095 0 1 0 105 0 11 lline A Fig 15 AGC on the microphone gain versus line current and Ragc 3 2 Supplies The TEA1099 provides three supply points VBB is the strong supply for most of the internal circuitry and the amplifiers VDD is a 3 35 V supply for the dialler or the microcontroller and MICS is a switched supply point for the electret microphones Moreover the TEA1099 can be powered by an external power supply connected at the input ESI Fig 16 shows the block diagram of the supply block 24 Philips Semiconductors TEA1099 Speech and Hand
53. e nnne trn nnnnr nass nnns 22 3 1 4 Automatic gain Control cec terii aa n Decade e eere 23 3 2 SUDPIICS aia fee ARN ADEE A EAS BAR AAAS Aaah ccc 24 3 2 1 SUpply VBB i ea i ee eee 25 9 2 2 Supply MD Dci ee eor ee eae A te tree nere ERE SAMA Mau Aish aisha eR eL 28 3 2 3 Microphone supply 29 CEE FANS e TK PM 29 3 3 1 Handset microphone amplifier eene enne nnn 31 3 8 2 0 MET E E 34 3 3 3 Handsfree microphone eene nnne nennen nnne nnn 36 3 3 4 Auxiliary transmit amplifier TXAUX sse nennen enne nnne nnns 38 93 4 HecelVO cx xor unum ep NAR a d a doce D dur Oc Ta aie ERU 40 3 4 1 Line receive amplifier 41 3 4 2 Earphone amplifier QR 45 3 4 3 Loudspeaker amplifier LSAO ssssssssssssssssee eene enne nennen nennen nene nnn 46 3 4 4 Auxiliary receive amplifier AUXO 48 3 4 5 Auxiliary microphone monitor amplifier nnn 53 3 5 Duplex Controler correria eee Tut eu gere eee niu tue te ure uuu mede 53 3 5 1 Signal and noise envelope 54 3 5 2
54. eference due to matching between internal and external resistors Furthermore the Rva resistor connected between REG and GND will slightly affect the apparatus impedance see section set impedance VLN V 14 1 E 3 10 E 3 100 E 3 1 E 6 R SLPE REG ohms Fig 10 Influence of the Rva resistor between REG and SLPE on Vin at 15 mA The DC slope of the voltage on pin LN is influenced by the Rslpe resistor as shown in fig 11 This value of Rslpe may be slightly modified even if the preferred one is 20 changing this value will affect more than the DC characteristics it also influences the gains the AGC characteristics the maximum output swing on the line the VBB slope start and stop currents and the low voltage threshold Ith 20 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 30 ohms E 000 E 0 10 E 3 20 E 3 30 E 3 40 E 3 50 E 3 60 E 3 70 E 3 80 E 3 90 E 3 100 E 3 lline A Fig 11 Influence of Rslpe on the DC characteristics 3 1 2 Line impedance Principle of operation The TEA1099 behaves like an equivalent inductance that presents a low impedance to DC and a high impedance Rp to speech signals Rp is an integrated resistance in the order of 25 kQ 15 It is in paralle
55. er block and the electret microphone supply are also enabled or disabled according to fig 54 In order to guarantee handset conversation mode when an other set is connected in parallel and when the line current is so low that the dialler or the microcontroller can t operate the values of the logic inputs are ignored when VBB has not been higher than 2 9 V or has fallen down below 2 5 V and the handset conversation mode is forced see 3 2 1 Input PD This input is active low it can be driven by an open drain structure because a pull up to VBB is included Nevertheless in case of I O structure on the microcontroller side a push pull output structure is recommended to polarize properly the input of the microcontroller when VBB varies no current will flow from VDD to VBB via this pin The threshold voltage level is 0 65 V typically with a temperature coefficient of 2 mV C The input voltage must stay within the limits GND 0 4 V to VBB 0 4 V Except in ring mode see fig 54 when PD is low all the internal consumptions are switched off only the supply block VDD is kept active in order to sink current from the tank capacitor connected at VBB Input MUTT This input is active low it can be driven by an open drain structure because a pull up to VBB is included Nevertheless in case of I O structure on the microcontroller side a push pull output structure is recommended to polarize properly the input of the microcontroller when VBB
56. etermining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgarint gain control factor varying from 1 at lline 15 mA to 0 49 at lline 70 mA when AGC function is applied see chapter 3 1 4 for details Using these typical values in the equation we find a gain equal to Gv ir reco 20 x log Avrx 29 7 8 atlline 15 mA DTMF has an a symmetrical high input impedance between pins DTMF and GND shared with the DTMF amplifier It is equal to 20 with a maximum tolerance of 15 The overall gain Gv dtmf reco of the receive amplifier from input DTMF to output RECO is given by the equation Gv dtmf reco 20 x log Avmfe Avmfe 0 017 x Rgarint Rrefint This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gv dtmf reco 20 x log Avmfe 16 5 dB at lline 15 mA RAUX has an a symmetrical high input impedance between pins RAUX and GND It is equal to 20 with a maximum tolerance of 15 The overall gain Gv raux reco of the receive amplifier from input RAUX to output RECO is given by the equation Gv raux reco 20 x log Avrrax Avrrax 0 088 x Rgarint Rrefint This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gv raux reco 20 x log Avrrax 2 3 dB at lline 15 mA Adjustments and performances 29 7 dB of receive gain between IR and RECO
57. frequency influence of temperature 43 35 Distortion on RECO versus input signal on 43 36 Distortion on RECO versus input signal on nennen nennen nnn 44 37 Distortion on RECO versus level with 5 load ssssssssssseeenn enne 44 EM DE Woisem C 45 39 Distortion on QR versus 1 46 40 Output level in ring mode versus input current at ESI 48 41 Auxiliary receive gain versus frequency influence of 50 42 Distortion on AUXO versus input signal on IR enne nnns 50 43 Distortion on AUXO versus input signal on HFRX ssssssssssssseeeeneeen nennen 51 44 Distortion on AUXO versus input signal on HFTX nnne 51 45 Distortion on AUXO versus level with 5 load nnns 52 46 Noise on AUXO with input at IR nnne nnne 52 47 Noise on AUXO with input at ssssssssssessseseeeennnenennennnnenrnn nnn nennen rins nn rennen nnns 53 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 48 Principle of the duplex Controller
58. g 32 Receive block diagram 40 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer LOGIC _ _ Fig 33 Block diagram related to AUXO 3 4 1 Line receive amplifier RECO Principle of operation According to the logic selection see fig 4 the line receive amplifier can get signal from three different inputs IR for line signals DTMF for confidence tone and RAUX as auxiliary input As can be seen from fig 32 the line receive amplifier itself is built up out of four parts three preamplifiers inputs IR DTMF and RAUX which realize a voltage to current conversion and an end amplifier which realizes the current to voltage conversion The RECO output of the TEA1099 has an internal impedance of 125 and is able to drive loads down to an impedance of 5 IR has an a symmetrical high input impedance between pins IR and LN It is equal to 20 with a maximum tolerance of 15 The overall gain Gv ir reco of the receive amplifier from input IR to output RECO is given by the equation Gv ir reco 20 x log Avrx Avrx 3 5 x Rgarint Rrefint x o 41 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer with Rgarint internal resistor realizing the current to voltage conversion typically 128 kQ with a spread of 15 Rrefint internal resistor d
59. ge is determined by the ratio of Rswr and Rstab see paragraph 3 5 4 Both Rswr and Rstab set internally used reference currents which are proportional to absolute temperature PTAT As already stated in 83 4 3 the volume control acts upon the receive preamplifier via the control of the voice switch As a result the loop gain of the handsfree set is kept constant when the volume of the receive path is adjusted However the voice switch is designed such that the volume control has no influence in Tx mode In the extreme case when the volume of the receive channel is reduced with the value of the switching range the 1099 virtually does not switch over In order to avoid inversion of the gain in Rx mode the volume control range of the TEA1099 cannot be larger than the switching range 3 5 4 Adjustments and performances of the duplex controller The adjustment of the duplex controller has to be performed according to the following receipe 1 Determine the switching range 2 Determine dial tone detector level 57 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 Determine sensitivity 4 Determine timings Ad 1 Determine switching range The switching range Asw is determined by the ratio of the two resistors Rswr and Rstab according to Asw dB 20 log Rswr Rstab The resistor Rstab has to be 3 65 kQ The value of the resistor Rswr can vary reas
60. he input IR which is left open With the antisidetone network connected to the input IR part of the microphone noise generated on the line will be added but thanks to the low microphone noise value the effect is almost negligible Fig 47 shows the noise on AUXO when the input is from MIC MIC Noise dBVp 95 000 E 0 10 E 3 20 E 3 30 E 3 40 E 3 50 E 3 60 E 3 70 E 3 80 E 3 90 E 3 100 E 3 line A Fig 46 Noise on AUXO with input at IR 52 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Noise dBVp 95 000 E 0 10 E 3 20 E 3 30 E 3 40 E 3 50 E 3 60 E 3 70 E 3 80 E 3 90 E 3 100 E 3 lline A Fig 47 Noise on AUXO with input at MIC MIC 3 4 5 Auxiliary microphone monitor amplifier When Group listening mode is selected the microphone signal is monitored with a fixed gain of 49 8 dB anda spread of 2 5 dB at the output TXOUT In this condition the end amplifier of the handsfree microphone channel is switched into high impedance output mode The channel between MIC MIC and TXOUT is built up out of two parts a preamplifier which makes a voltage to current conversion followed by an end amplifier which realizes the current to voltage conversion The output is biased at 2 Vd and can drive up to 300 uA rms and the
61. high it can be driven by an open drain structure because the pull down is included the threshold voltage level is 0 65 V typically with a temperature coefficient of 2 mV C The input voltage must stay within the limits GND 0 4 V to VBB 0 4 V When using a standard dialler for only basic applications handset mode handsfree mode and dialling modes this input can be left open 3 6 2 Connections The following table gives the details of the connections which are enabled according to the logic inputs and some ideas of applications which are foreseen 64 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer _ _ LOGICINPUTS CONNECTIONS APPLICATIONS HOMME ME peH d t esie emissis _ efo xf a UU Eee eee DTMF sLN CT gt RECO Tel Set DTMF dialling MICS QR MIC gt AUXO RAUX gt RECO Cordless intercom with handset MICS QR ar gt AUXO RAUX gt RECO MIC gt LN IR gt RECO IR gt AUXO_ Handset en A M EN STXOUT MICS UEM EM ET 1 MIC gt LN MIC gt TXOUT gt LN MIC gt TXOUT TXAUX LN IR gt AUXO Conversation with A M RF interface TXAUX gt LN IR gt AUXO RAUX gt RECO TXIN gt TXOUT HFTX gt LN Cordless Handsfree in mobile PAF gt RECO HFRX gt AUXO 1 RAUX gt HFRX gt LSAO Listenning on loudspeaker TXAUX gt LN IR gt AUXO
62. ier and the input current on ESI necessary to get this value of VBB The difference between these currents is available as power for the loudspeaker amplifier 27 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 9 0E 3 8 37E 03 8 0E 3 7 0E 3 2 f 6 62 03 6 0E 3 AUS 2 488 03 4 0E 3 3 16E 03 3 0E 3 35 i Eu i VBB V Current consumption on VBB 7 Total input current on ESI v Fig 18 Current consumption on VBB in ring mode versus VBB 3 2 2 Supply VDD Principle of operation The supply block VDD is fed from VBB so VDD is typically 0 25 V lower than VBB and clamped typically at 3 35 V Nevertheless the block VDD can be externally supplied if the external source provides a current lower than 60 pA VDD is also clamped at 3 35 V if this current is higher than 200 pA the voltage on VDD follows the voltage of the external source These two modes allow either the supply of the dialler with a trickle current without any additional zener diode or the supply from an external regulated power supply without too much current consumption The output capability of VDD is typically 3 mA when ESI is supplied or when the line current is higher than 11 mA with no extra consumption on VBB in line powered mode In line powered mode this output capability is reduced progressively d
63. ine impedance Example Let s optimize for a theorical equivalent average line impedance shown in Fig 14 1265 Q 210 0 140 nF Fig 14 Equivalent average line impedance For compatibility of the capacitor value in Zbal with a standard capacitor value from the E6 series 220 nF 140 220 0 636 For Rast2 a value of 3 92 has been chosen So using the previous equations we can calculate Zbal Rast1 Rast3 We find Rast1 130 Rast3 390 and for Zbal 130 Q in series with 220 nF 820 The attenuation of the receive line signal between LN and IR can be derivated from the following equation Vir Vin Zir Rast2 Rasti Zir Rast2 If Rast2 Rast3 Zbal With the values used in this example it gives 32 dB at 1 kHz Zir is the receive amplifier input impedance typically 20 kO 3 1 4 Automatic gain control Principle of operation The TEA1099 performs automatic line loss compensation The automatic gain control varies the gains according to the line DC current of the amplifiers which send on line except the DTMF one and of the amplifiers which receive from line at pin IR To enable this AGC function the pin AGC must be connected to the pin LN For line currents below a current threshold Istart typically 23mA the gain control factor is equal to 1 giving the maximum value to the gains If this threshold current is exceeded the gain control factor reduced and then
64. ing machine applications and MIC MIC e g intercom or answering machine applications As can be seen from fig 33 the auxiliary receive amplifier itself is built up out of five parts four preamplifiers inputs IR HFRX HFTX and MIC MIC which realize a voltage to current conversion and an end amplifier which realizes the current to voltage conversion The AUXO output of the TEA1099 has an internal impedance of 125 and is able to drive loads down to an impedance of 5 IR has an a symmetrical high input impedance between pins IR and LN shared with the IR to RECO amplifier It is equal to 20 with a maximum tolerance of 15 The overall gain Gv ir auxo of the auxiliary receive amplifier from input IR to output AUXO is given by the equation Gv ir auxo 20 x log Avrax Avrax 6 66 x Rgara Rrefint x with Rgara internal resistor realizing the current to voltage conversion typically 96 3 kQ with a spread of 15 Rrefint internal resistor determining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgara 48 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer gain control factor varying from 1 at lline 15 mA to 0 49 at 70 mA when AGC function is applied see chapter 3 1 4 for details Using these typical values in the equation we find a gain equ
65. it and receive gain is kept constant This is done to keep the loop gain of the handsfree telephone set constant see also the introduction 1 The switch over behavior of the voice switch is shown in fig 51 56 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer dB Rvol 0 Rvol 6k Rvol 20k Rvol 50K 30 25 20 23 28 0 3 0 2 0 1 0 0 1 02 WMVewt idt V 93 Fig 51 Behavior of the voice switch When the voltage on SWT is more than 180 mV below the voltage on IDT the TEA1099 is fully switched to Tx mode gain of the transmit path at maximum and gain of the receive path at minimum When the voltage on SWT is more than 180 mV above the voltage on IDT the TEA1099 is fully switched to Rx mode gain of the receive path at maximum and gain of the transmit path at minimum The TEA1099 is considered to be in Ix mode when the voltage on SWT equals the voltage on IDT When the capacitor Cswt is charged or discharged the voltage on SWT varies and as a result the voice switch will smoothly switch over between the modes keeping the sum of the transmit and receive gains constant The difference between the maximum and the minimum gain of the receive or transmit preamplifiers is called the switching range This ran
66. l with the external network realized by Zimp and Cimp Thus in the audio frequency range the apparatus impedance called set impedance is mainly determined by the Zimp resistor Fig 12 shows an equivalent schematic for the set impedance LN Leq Creg x Rslpe x Rp Rp z internal resistor GND Fig 12 Equivalent set impedance 21 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Adjustments and performances When decreasing the reference voltage Vref a resistor is connected between GND and REG in parallel of Rp see fig 12 so slightly modifying the impedance If complex set impedance is required Zimp is a complex network if a purely resistive set impedance is required Zimp is a resistor The value of the capacitor Cimp has to be high enough advised value of 22 in order to have an impedance negligible compare to Zimp or it may be used to generate the capacitive part of a complex impedance assuming that DC decoupling is kept 3 1 3 Anti sidetone network Principle of operation To avoid the microphone signal to come back with a too high level in the receive channel the anti sidetone circuit uses the microphone signal from pin SLPE which is in opposite phase to cancel the microphone signal at the IR input of the receive amplifiers The anti sidetone bridge principle already used for the TEA106x or the TEA111x families is used in a reverse
67. maximum output swing is VBB 0 8V An external antihowling circuit is shown in 5 fig 63 while the block diagram of the Group listenning application is shown fig 57 3 5 Duplex controller In this chapter the principle of operation of the duplex controller will be described as well as its adjustments and performances This will be done with the help of fig 48 Nevertheless the duplex controller part is enabled only when VBB becomes higher than 2 9 V see 3 2 1 53 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer from microphone from preamplifier input TXIN LOGIC BLOCK to microphone preamplifier TXIN Ctsen Rtsen Cswt l d 5 lt 1 DECISION LOGIC VOICE SWITCH Crsen Rrsen to receive preamplifier HFRX from loudspeaker amplifier input HFRX from volume control Fig 48 Principle of the duplex controller As can be seen in fig 48 the duplex controller is built up out of signal and noise envelope detectors decision logic and a voice switch The signal and noise envelope detectors determine the signal envelopes and the noise envelopes of both the transmit and receive signal These envelopes are used by the decision logic to determine into which mode the TEA1099 has to switch over Tx Rx or Ix mode The logic charges and discharges the capacitor Cswt and the resulting voltage on pin SWT controls the voice swi
68. miconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 3 DESCRIPTION OF THE TEA1099 This chapter describes in detail the six blocks of the speech handsfree circuit TEA1099 the line interface 3 1 the supply 3 2 the transmit block 3 3 the receive block 3 4 the duplex controller 3 5 and the logic block 8 6 For each block the principle of operation is described and its adjustments and performances are discussed All values given in this chapter are typical and at room temperature unless otherwise stated For more details see TEA1099 device specification All the curves shown in this section result from measurement of typical samples using the schematic of fig 66 All the component names refer to the basic application of the IC shown in appendix fig 64 3 1 Line interface 3 1 1 DC characteristics Principle of operation The TEA1099 generates a stabilized voltage called Vref between pins GND and SLPE This reference voltage temperature compensated is typically 3 7 V for line currents between 10 and 18 mA and 6 15 V for line currents between 46 and 140 mA For line currents between 18 and 46 mA Vref increases proportionally to this line current with a slope of typically 87 5 so from typically 3 7 to 6 15 V The voltage at pin REG is used by the internal regulator to generate the stabilized Vref voltage and is decoupled by a capacitor Creg connected to LN
69. ming Ridt 2 2 MQ time constant 4xRidtxCswt Fig 55 Steps in the design flow of the TEA1099 70 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 5 APPLICATION EXAMPLES In this chapter some general block diagrams are provided to show the integration method of the TEA1099 in different terminal applications Moreover a demoboard OM5846 is available As the TEA1099 may be used in various applications this demoboard includes only the TEA1099 with its basic environment Its schematic is shown in fig 64 while its component placement diagram is in fig 65 On this schematic the components which are connected with dotted lines are for RFI immunity purpose only Moreover a proposal of external antihowling circuitry is included on the layout of the PCB its components are not equipped with its input at TXOUT and output on DLC 71 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer VDD NM UBA1702 Va PCD33xx VDD LN SUPPLY MIC PUR Fig 56 Basic handsfree application 72 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer EJ VDD UBA1702 ARE PCD33xx NI SUPPLY TIME CONSTANT AND ATTENUATOR Fig 57 Group listenning conversation with antihowling 73 Phili
70. mplifier and is stabilized by the capacitor Creg connected at pin REG The line current is sensed across the resistor connected between pins LN and SLPE An AGC function is provided when pin AGC is connected directly or through a resistor to LN The impedance of the apparatus is set by a network connected between LN and GND through a decoupling capacitor Supply The circuit can be supplied from the line and or by an external supply It provides a stabilized 3 35 V supply point for peripherals which can also be externally supplied in trickle mode The TEA1099 can be switched into a low power consumption mode with the pin PD Transmit The transmit signal can come from four preamplifiers handset microphone MIC MIC handsfree microphone TXIN to TXOUT and HFTX the auxiliary transmit TXAUX and the DTMF The selection is made by the logic block The signal reference is GNDTX a clean ground which has to be connected to GND for the handsfree microphone The inputs have to be coupled by means of capacitors All the gains have a fixed value except the gain of the handsfree microphone amplifier which is set with Rgatx Receive The signal received from the line is amplified from pin IR to pin RECO and or to the auxiliary output AUXO The input IR has to be coupled by means of a capacitor From pin RECO the signal is sent to the earphone amplifier at pins GARX and QR and to the input of the duplex controller HERX The gain of the ear
71. n be used to adjust the loudspeaker amplifier curve A capacitor Cgals of at least 150 pF is recommanded in ringer mode The output drive capability at pin LSAO is typically 300 mApeak The noise level at the output LSAO is 79 dBVp at a gain of 28 dB and with the input HFRX left open Out of pin VOL a current lvol set by Rstab is flowing which is proportional to the absolute temperature PTAT At room temperature this current is around 5 pA Together with the resistance of the potentiometer the current Ivol creates a PTAT voltage on pin VOL This PTAT voltage is processed by the volume control block as a result a temperature independent volume reduction of the output receive signal of 3 dB is obtained at approximately every increase of 1900 Q of the potentiometer resistance This means that a linear potentiometer can be used to control the volume logarithmically thus in dB With the advised value of 22 kO the maximum gain reduction of the volume control is more than 30 dB However this maximum gain reduction is limited by the switching range see 3 5 When the resistance of the potentiometer is zero the receive gain is maximum in Rx mode When digital volume control is desired the switches can be either MOSFETs or analog switches with very low DC and AC resistance Due to saturation voltage it is advised not to use bipolar transistors as switches In line powered condition matching between operating current range and impedance of loud
72. n in fig 32 the input of the receive channel pin HFRX is a symetrical and the signal has to be referenced to GND The input HFRX is connected via a decoupling capacitor to the receive output RECO In ring mode the melody signal is directly connected to pin HFRX via a decoupling capacitor The output of the loudspeaker amplifier is pin LSAO As can be seen in fig 32 the channel to the loudspeaker amplifier is built up out of two parts a preamplifier and an end amplifier The gain of the preamplifier is determined by the duplex controller block The gain of the end amplifier is determined by the external feedback resistor Rgals The overall gain Gvlsao of the loudspeaker amplifier channel from input HFRX to output LSAO is given as Gvlsao 20 log Avis Avls 0 35 x Rgals Rstab This gain is not affected by the AGC using these typical values in the equation we find a gain equal to Gvlsao 20 x log Avis 27 8 dB when Rgals 255 With Rstab being the resistor at STAB of 3 65 kO Via the volume control input VOL the volume of the receive signal can be adjusted by the external potentiometer connected to pin VOL By changing the potentiometer resistance the gain of the preamplifier varies through the duplex controller Volume control doesn t affect the transmit gain in Tx mode The loudspeaker amplifier is enabled only when VBB becomes higher than 2 9 V when it is it can be automatically disabled if VBB falls down belo
73. n pins VBB and GND the advised value is 470 a higher value would delay the start up time of the system When an external voltage source is provided at ESI a diode is necessary in order to allow VBB to take a value higher than the value of this source when the line current is high enough e g 3 3 V at ESI and gt 46 mA of line current which provides VBB at 5 35 V and to prevent VBB from collapse if this supply is temporarely out of order If an Rva resistor is connected between REG and GND to reduce the line voltage the 0 7 V voltage difference between SLPE and VBB is reduced then the power available for the loudspeaker amplifier is dramatically reduced and even can t exist if the remaining voltage is lower than 0 3 V The low VBB condition detector enables the handsfree part the loudspeaker amplifier and the logic block when VBB becomes higher than 2 9 V The loudspeaker amplifier is disabled when VBB falls down below 2 7 V while the logic block is disabled when VBB falls down below 2 5 V When VBB has fallen below 2 5 V in order to indicate that the handset conversation mode is forced the pin HFC is pulled to GND These hysteresis allow a stable operation of the loudspeaker amplifier in low supply condition because if there is no change in the supply condition the dynamic limiter should avoid VBB to fall below 2 7 V Fig 18 shows the current consumption on VBB in ringer mode when no signal is sent to the loudspeaker amplif
74. nF Chfx 36 DLC R HFTX 0 47 pF 470 nF 27 GATX Rgatx 30 1 100 pF 26 TXOUT Ctxin 5g BMICP TXIN 470 nF 4 Rtsen Ctsen TSEN 100 nF 3 Ctenv VEDI 42 ii R RAUX tT RAUX 470 nF 470 nF 38 2 Rtnoi Ctnoi E TNOI Er 00 4 7 uF 5 Rrnoi Crnoi HFC HFC RNO 00 4 7 pF MOTT 40 MUTT 7 u MUTR MUTR Ab ait S Rrs Cr AUXC AUXC 6 sen rsen Rstab 21 10kQ 100 nF STAB 24 Cswt 3 65 SWT J Rswr 25 3 Ridt 220 nF SWR IDT 365 22 Fig 66 Curve ref board of the TEA1099 88
75. ne amplifier has symmetrical high input impedances typically 70 2 times 35 kQ between pins MIC and MIC with maximum tolerances of 15 As can be seen from fig 20 the microphone amplifier to LN is built up out of two parts a preamplifier which realizes a voltage to current conversion and an end amplifier common with the other three transmit paths which realizes the current to voltage conversion The overall gain Gv mic In of the microphone amplifier from inputs MIC MIC to output LN is internally set and given by the following equation Gv mic In 20 x log Avmic Avmic 5 7 x Rgasint Rrefint x Ri Zl Rslpe with Ri the AC apparatus impedance Rcc Rp typically 620 25 Rgasint internal resistor realizing the current to voltage conversion typically 27 6 kQ with a spread of 15 Rrefint internal resistor determining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgasint Zl load impedance of the line during the measurement gain control factor varying from 1 at lline 15 mA to 0 49 at lline 70 mA when AGC function is applied see chapter 3 1 4 for details Using these typical values in the equation and assuming Zline 600 we find a gain equal to Gv mic In 20 x log Avmic 44 1 dB at lline 15 mA The AGC gain control acts on the microphone preamplifier stage modifying its transconductance Moreo
76. ng time of around 2 seconds is obtained To have a clearly determined idling timing it is advised not to use a capacitor with a high leakage current When the calculated timing settings are implemented subjective tests with real telephone lines will be necessary to be sure that the optimal timings have been set 60 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Miscellaneous Idle mode gain When a handsfree telephone set is used at one end of the line and a conventional set at the other end the user of the conventional set may think that the line is cut when the handsfree set stays in receive mode while no signal on the line is present This is avoided when the handsfree set switches over to idle mode This mode is incorporated in the TEA1099 and is placed exactly at mid attenuation between transmit and receive mode When it is desired to have an idle mode which is closer to transmit than receive mode the circuit of fig 52 can be applied SWT Ridt Rdiv1 IDT 2 2 MQ Cswt Rdiv2 220 nF GND Fig 52 Circuit for shifting the idle mode With the circuit of fig 52 in idle mode the voltage on SWT will not go to the voltage on IDT but to the voltage on IDT minus the voltage drop over Rdiv1 The voltage drop over Rdiv1 determines the shift of the idle mode in dB This shift can be read from fig 51 when the voltage drop over Rdiv1 is taken as the X axis v
77. oise envelope on RNOI or TNOI Signal envelope on TENV or RENV Signal on TSEN or RSEN t Fig 49 Typical behavior of the signal and noise detectors In fig 49 it is shown that when the input signal raises quickly the envelope signal follows immediately and the noise envelope slowly follows the envelope signal When the input signal decreases the envelope signal follows immediatly but nevertheless less quickly than when it raises the noise envelope follows immediatly the decrease of the envelope signal and never crosses it 3 5 2 Decision logic The signal and noise envelopes of the transmit and receive signal are used by the decision logic to determine in which mode the TEA1099 has to be The output of the logic is a current source which charges or discharges the capacitor Cswt at pin SWT If the logic determines Tx mode the capacitor Cswt is discharged with 10 A When Rx mode is determined Cswt is charged with 10 pA When Ix mode is determined the current source is zero and the voltage on SWT becomes 55 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer equal to the voltage on pin IDT via the current provided through the resistor Ridt The time constants of the duplex controller are therefore determined by the combination of the internal current sources the capacitor Cswt and the resistor Ridt As can be seen in fig 48
78. oltage Supply for electret microphones Reference current adiustment Switching range adiustment Loudspeaker amplifier volume adiustment Switching timing adiustment Idle mode timing adiustment Handsfree microphone amplifier output Handsfree microphone qain adiustment Handsfree microphone amplifier input Ground reference for microphone amplifiers Inverting HS microphone input Non inverting HS microphone input Dual Tone Multifrequency input Earpiece amplifier outout Earpiece amplifier gain adjustment Receive amplifier output Transmit input for line amplifier or auxiliary receive amplifier Loaic input Power down input Loaic input Loaic input Loaic input Auxiliary receive input Auxiliary transmit input Auxiliarv output 12 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer In fig 2 it can be seen that the IC consists out of six main parts the line interface the supply block the transmit block the receive block with the loudspeaker amplifier the duplex controller and the logic block which controls the IC These blocks are shortly described below including the function of the external components The detailed description will follow in chapter 3 Line interface The TEA1099 generates a stabilized voltage called Vref between pins GND and SLPE This reference voltage is line current dependant in order to get optimum supply for the loudspeaker a
79. onably between 20 kQ and 1 5 MQ resulting in a switching range between 15 dB and 52 dB With Rswr of 365 kQ the switching range is typically set to 40 dB The switching range is calculated out of the loop gain Aloop In a handsfree application the loop gain has to be smaller than one lt 0 dB and can be calculated as follows Aloop Atx1099 Ast Arx1099 Aac Asw with 1099 sending gain of the TEA1099 TXIN to TXOUT HFTX to LN Ast electrical sidetone Arx1099 receive gain of the TEA1099 LN to IR to LSAO Aac electro acoustic coupling from loudspeaker to microphone LSAO to TXIN Asw switching range In this calculation the worst case has to be taken for Ast and Aac Furthermore for safety it is advised to choose Asw large enough to compensate spreads margin from 8 to 15 GB The electrical sidetone is the difference in dB between the wanted receive signal on the TEA1099 and the unwanted part of the transmit signal received while having an equal signal level on pin LN for both the transmit and the receive signal Ast is dependent of frequency and connecting conditions of the set line length line impedance The acoustic coupling is dependent on the environment of the telephone set for the determination of Aac the worst condition has to be searched If a certain minimum volume control range is required the switching range must not be chosen smaller It is also possible to determine the switching range
80. own to about 1 mA at 7 mA of line current depending on the current drawn at MICS In power down or ringer modes VDD regulator is still working and provides 3 35 V as long as VBB is higher than 3 65 V Moreover the current consumption of VDD is lower than 150 nA when VDD lt 1 5 V in order to allow supply of the dialler or microcontroller with a trickle current Adjustments and performances A capacitor Cvdd must be connected between pins VDD and GND even if this output is not functionaly used in order to keep a small start up time its value must be limited to a few 10 uF In power down mode DC dialling or flash the block VDD is still supplied from VBB and the capacitor Cvbb is the main tank When an external voltage source is provided a diode in series is mandatory if this source is lower than 3 5 V or if it may be switched off If it is higher than 3 5 V the current consumption is less than 200 pA 28 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Fig 19 shows the typical current consumption on VDD in trickle mode when VBB O IVDD A 1 E 6 100 E 9 13nA 10 E 9 1 E 9 1 4 1 45 T5 1 55 1 6 1 65 1 7 1 75 1 8 VDD V Fig 19 Current consumption on VDD at VBB 0 3 2 3 Microphone supply MICS Principle of operation The electret microphone supply
81. p Set passive impedance The BRL is adjusted with the impedance network connected between LN and GND Rec Rz Cz in series with Ccz Sidetone Adjust Zbal Rbal1 Rbal2 Cbal according to the line characteristics AGC Internally defined the characteristics Istart and Istop can be shiftted to higher line currents with an external Ragc resistor connected between AGC and LN In case it is necessary to shift Istart and Istop to lower current values the value of Rslpe may be slightly increased proportionally see 83 1 4 TEA1099 transmit and receive gains in handset mode Handset microphone gain The microphone gain of the application has to be adjusted before entering pins MIC MIC of the TEA1099 It can be reduced by using the resistor Rtx3 which forms a bridge attenuator with Rtx1 and Rtx2 Ctx1 Ctx2 form a high pass filter with Rtx1 Rtx2 in series with the input impedance at MIC MIC A capacitor Cmich forms a low pass filter with the impedance of the microphone and the resistors Rmicp Rmicm The gain between MIC MIC and LN is 44 1 dB on 600 Receive gain Receive gain of the handset has to be adjusted with earphone amplifier with the resistor Re1 A capacitor Cgar in parallel with Re2 forms a low pass filter stability is ensured with capacitor Cgars 10 x Cgar between pins GARX and VEE The gain between IR and RECO is fixed at 29 7 dB 68 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note
82. phone amplifier is set with 2 resistors From HFRX the signal can be sent to the loudspeaker amplifier pins GALS and LSAO and the volume can be adjusted by means of the potentiometer connected between input VOL and GNDTX the gain of the loudspeaker amplifier is set by the resistor Rgals The signal from the auxiliary input RAUX can also be sent to RECO Moreover the auxiliary output AUXO can get its signal from IR HFRX through the duplex controller MIC MIC or HFTX Duplex controller From both the transmit and receive signals signal and noise envelopes are made The transmit signal envelope is on pin TENV and the receive one on pin RENV The transmit noise envelope is on pin TNOI and the receive one on pin RNOI The timing of the envelopes can be set by the capacitors Ctenv Ctnoi Crenv and Crnoi The sensitivity of the envelope detectors can be set by means of the RC combinations Rtsen with Ctsen for the 13 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer transmit envelope and Rrsen with Crsen for the receive one The resistors set the sensitivity and the capacitors block the DC component creating also high pass filters The decision logic of the duplex controller determines into which mode Tx Rx or Ix mode the set has to switch over The timing for switching to the Tx or the Rx mode is determined with the capacitor Cswt The timing for switching to
83. phone company QR Earphone amplifier output of TEA1099 RAUX Auxiliary receive input RECO Receive output from line 83 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer REG RENV Rexch Rgatx Ridt Rload Rmicm p b RNOI Rp Rrsen RSEN Rslpe Rstab Rswr Rtnoi Rtsen Rva Rvol Rx mode SLPE STAB SWR SWT TENV THD Tidt TNOI TSEN TXAUX TXIN TXOUT Tx mode Filter capacitor of the equivalent inductor connection pin of the TEA1099 Receive signal envelope timing adjustment pin Bridge resistance of exchange Radio frequency interference Resistor setting receive earphone amplifier gain Resistor setting base microphone amplifier gain Resistor setting Ix mode timing Loudspeaker equivalent load resistor Resistors setting microphone sensitivities Receive noise envelope timing adjustment pin Internal resistance between LN and REG Resistor setting sensitivity of the receive envelopes Receive signal envelope sensitivity adjustment pin Resistor setting slope of the DC characteristic of TEA1096 Resistor setting an internally used PTAT current Resistor setting switching range Resistor increasing microphone speech noise threshold Resistor setting sensitivity of the transmit envelopes Voltage adjustment resistor Volume control potentiometer Receive mode DC slope pin of TEA1099 Reference current pin Switching range adjustment pin S
84. ps Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer RING DETECT RF INTERFACE OUTPUT Fig 58 Cordless conference with line base and mobile 74 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer RING DETECT uc j SUPPLY DTMF fe RF INTERFACE TAUX Fag OUTPUT a RF INTERFACE HFTX INPUT TXOUT Fig 59 Cordless handsfree conversation in mobile 75 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer SUPPLY CODEC OUTPUT FOR OUTGOING MESSAGE CODEC INPUT FOR RECORDING Fig 60 Answering Machine on line 76 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer RING DETECT RF INTERFACE RF INTERFACE Fig 61 Cordless intercom between mobile and base handset 77 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer RING DETECT MODEM OUTPUT RF INTERFACE OUTPUT RF INTERFACE INPUT CODEC OUTPUT TXOUT ccu M MEM ME OUTGOING MESSAGE CODEC INPUT FOR RECORDING Fig 62 Application with Fax Cordless and Answering Machine 78 Philips Semiconductors T
85. rmonic distortion However the microphone input signal is also used by the duplex controller At 7 mVrms at the input the positive part of the signal on pin TSEN starts clipping which might influence the switching behavior It is therefore advisable to keep the microphone input signal below this level The TXOUT output of the TEA1099 has an internal impedance of 200 and its output drive capability is 20 pArms The output noise at TXOUT of the TEA1099 is 103 dBVp psophometrically weighted at a gain of 15 dB With the sending gain between HFTX and LN set at 35 dB total handsfree transmit gain of 50 dB the noise level on the line will be 66 dBmp In Tx mode the noise level will be at its maximum In Ix mode and Rx mode the noise at TXOUT will be lower because the contribution of the preamplifier is reduced However the bottom level of the sending noise at TXOUT is limited by the end amplifier and is about 111 dBVp So in Ix mode the noise level on line will be 74 dBmp 37 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer The input of the HFTX amplifier is biased at 2 Vd and can handle signals up to 95 mVrms to LN with less than 2 THD Fig 29 shows the distortion on line versus the rms input signal at lline 70 mA THD 2 18 16 14 12 1 0 4 EE 02 HFTX Inpu
86. sfree IC with Application Note auxiliary inputs output and analog multiplexer from external i supply Cvbb VBB ESI Starter E p Voltage Supply Tline management stabilizer slope low voltage current detection VDD external VDD supply voltage supply low VBB condition detection MICS electret microphone supply Cmics Fig 16 Block diagram of the supply block 3 2 1 Supply VBB Principle of operation VBB can be either line powered or externally powered at ESI when both supplies are available the strongest of the two is automatically selected and used internally When VBB is purely line powered its value is correlated with the value of the line voltage and then of the line current as follows e below9 mA low voltage area 25 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 9to18mA 3V e 18t0 46 mA VBB increases with a slope of 84 Q from 3 to 5 35 V e above 46 mA VBB 5 35 V The correlation between line voltage and VBB is done in order to get a voltage difference between Vslpe and VBB of at least 0 7 V in order to guarantee a good power supply efficiency when AC signal is present on SLPE On the block diagram two PNP transistors drive the line current either to VBB or to GND when the voltage on SLPE is higher than VBB 0 3 V the current is driven to VBB
87. speaker is important below approximately 27 mA a 32 loudspeaker provides more power than a 25 one Fig 17 shows the output level on LSAO versus line current 16 and 50 loads in series with 220 uF in handsfree mode and nominal line powered conditions When an external power supply is connected at pin ESI the LSAO can drive loudspeakers with an impedance down to 8 In an 8 loudspeaker configuration the output swing can be optimized by shifting slightly the polarization with a 2 2 MO resistor connected between pins GALS and VBB Fig 40 shows the output level sine wave on different loads in series with 220 uF in ring mode versus input current at ESI 47 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Plsao mW 200 180 160 140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 Plsao 50hms Plsao 150hm 7 gt Plsa 270hm Plsa 100hm lesi mA Fig 40 Output level in ring mode versus input current at ESI 3 4 4 Auxiliary receive amplifier AUXO Principle of operation According to the logic selection see fig 4 the auxiliary receive amplifier can get signal from four different inputs IR for line signals HFRX through the duplex controller in receive HFTX from TXOUT and the duplex controller e g intercom or answer
88. t its maximum and the gain of the microphone amplifier is reduced 3 Idle mode Ix mode the gains of the handsfree microphone path and of the receive path are halfway their maximum and reduced values The difference between the maximum gain and the reduced gain is called the switching range This report gives a detailed description of the TEA1099 and its basic application The description is given by means of the block diagram of the TEA1099 2 and by discussing every detail of the sub blocks 3 The application is discussed by giving a guideline for application the application cookbook 4 and by giving an application example 5 EMC aspects are also discussed 6 The appendix contains a list of abbreviations and the demoboard application diagram of the TEA1099 Note the values of parameters given in this application note are as accurate as possible but please refer to the last product specification for final ones Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 2 BLOCK DIAGRAM In this chapter the block diagram of the TEA1099 is shown by means of fig 2 The pinning of the TEA1099 is given by means of fig 3 A short description of the block diagram is given including the function of the external components LOGIC PD to uC or INPUTS dialler HFC from uC or MUTT dialler MUTR AUXC STAB INTER
89. t level Vrms Fig 29 Distortion on line versus HFTX input level 3 3 4 Auxiliary transmit amplifier TXAUX Principle of operation The auxiliary transmit amplifier has an a symmetrical high input impedance of 20 kO between pins TXAUX and GND with a maximum spread of 15 The auxiliary transmit amplifier is built up out of two parts a preamplifier which realizes the voltage to current conversion and the same end amplifier as the handset microphone amplifier The overall gain Gv txaux In of the auxiliary transmit amplifier from input TXAUX to output LN is given by the following equation Gv txaux In 2 20 x log Avtxa Avtxa 0 151 x Rgasint Rrefint x Ri Zl Rslpe x with Ri the AC apparatus impedance Rcc Rp typically 620 25 Rgasint internal resistor realizing the current to voltage conversion typically 27 6 with a spread of 15 Rrefint internal resistor determining the current of an internal current stabilizer typically 14 7 with a spread of 15 correlated to the spread of Rgasint Zl load impedance of the line during the measurement gain control factor varying from 1 at lline 15 mA to 0 47 at 70 mA when AGC function is applied see chapter 3 1 4 for details 38 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Using these typical values in the equation and assuming Zline 600 we fin
90. tch The voice switch switches over the TEA1099 between the three modes while keeping the loop gain constant In paragraphs 3 5 1 to 3 5 3 the principle of operation of the three parts is given In paragraph 3 5 4 the adjustments and performances of the complete duplex controller are given 3 5 1 Signal and noise envelope detectors The signal and noise monitors of the transmit and receive channels are globally the same Therefore the principle of the detectors will be explained with the help of one of them the signal and noise detector of the transmit channel The microphone signal on pin TXIN is sent to the first stage of the detector see fig 48 The first stage amplifies the microphone signal from pin TXIN to pin TSEN with an internal gain of 40 dB Via the RC combination RtsenCtsen the signal on TSEN is converted into a current This conversion determines the sensitivity of the 54 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer envelope detector The current is logarithmically compressed and internally converted to a voltage which represents the compressed microphone signal At room temperature an increase of the microphone signal with a factor of 2 will increase the signal envelope with 18 mV if the current through TSEN stays between 0 8 and 160 Arms Outside this region the compression is less accurate The compressed microphone signal is buffered
91. the envelopes are not used directly by the decision logic First to have a clear choice between signal and noise the signal is considered as speech when its envelope is more than 4 3 dB above the noise envelope At room temperature this is equal to a voltage difference of 13 mV This so called speech noise threshold is implemented in both the receive and the transmit channel At the end of paragraph 3 5 miscellaneous a way to increase this threshold is discussed Second the signal on TXIN contains the signal of the local talker as well as the signal coming from the loudspeaker acoustic coupling In Rx mode the contribution of the loudspeaker overrules the contribution of the local talker As a result the signal envelope on TENV is mainly formed by the loudspeaker signal to correct this an attenuator is placed between TENV and the TENV RENV comparator The attenuation equals the attenuation applied to the microphone amplifier gain Thus when the TEA1099 is in Rx mode the attenuation equals the switching range Third when a dial tone is present on the line without measures this would be recognized as noise after some delay because its level is constant As a result the TEA1099 would go to Ix mode and the user of the set would hear the dial tone fade away Therefore a dial tone detector is incorporated which doesn t consider input signals as noise when they have a level higher than the dial tone level The dial tone level represented by Vdt
92. tic of the demobOard ioter tt eben etd aecebe b resedit beat 86 Fig 65 component placement diagram of the 87 Fig 66 Curve ref board of the TEA1099 sessssssssssssssseessse nennen nennen 88 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer 1 INTRODUCTION The TEA1099 is a circuit which offers a handsfree function with the line interface and the normal handset interface it also incorporates auxiliary amplifiers combined with switches and a logic control block It incorporates a base microphone amplifier a volume control of the loudspeaker amplifier and a duplex controller with signal and noise monitoring on the transmit and receive channels A power supply block extracts power from the line in an optimized way for the loudspeaker amplifier furthermore this supply block can be powered from any external supply A stabilized 3 35 V supply is available for peripherals This makes the TEA1099 suitable as the core of a multifunction telecom terminal such as cordless telephones answering machines or fax machines The function of the handsfree application is illustrated with the help of fig 1 Line acoustic coupling sidetone Fig 1 Handsfree telephone set principle The left side of fig 1 shows a principle diagram of the line
93. ver the logic block enables or disables the preamplifier according to the selected mode see fig 4 The inputs are biased at one Vd The input of this microphone amplifier is able to handle AC signals up 18 mVrms with less than 2 total harmonic distortion The microphone amplifier to TXOUT is used for monitoring the microphone signal in order to built an external antihowling circuit 83 4 5 It is also built up out of two parts a preamplifier which realizes a voltage to current conversion and an end amplifier common with the handsfree microphone amplifier which realizes the current to voltage conversion The overall gain Gv mic txout of the microphone amplifier from inputs MIC MIC to output TXOUT is fixed and given by the following equation Gv mic txout 20 log 6 4 Rgatxint Rrint Rgatxint internal resistor typically 80 with a spread of 15 Rrint internal resistor typically 1 66 kQ with a spread of 15 Adjustments and performances Fig 21 shows the typical frequency response of the microphone amplifier of the TEA1099 31 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer Igain dB 46 44 95 dB 45 9 ca ied gt 7 44 65 dB f 44 2 43 E 42 1 41 40 10 100 1000 10 000 gan25 ___ gain75 g
94. w 2 7 V but this should not happen in normal line conditions because of the dynamic limiter see 3 2 1 A ringer mode is available where only the channel from HFRX to LSAO is enabled this mode can be used with a Switch Mode Power Supply converting the ringing signal into a DC supply applied at pin ESI In this mode a 46 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer square wave melody signal has to be applied at pin HFRX with an advised amplitude of 200 mVpp lower than 500 mVpp The volume control is not operating in this mode Adjustments and performances The input signal for the loudspeaker channel has to be coupled via a decoupling capacitor Together with the input impedance of 20 kO at HFRX a first order high pass filter is introduced which can be used to adjust the receive curve and or to reduce any low frequency unwanted signal coming from the line The input HFRX is biased at 2 Vd and can handle signal up to 580 mVrms with a total harmonic distortion of 2 The output LSAO must be connected to the loudspeaker via a decoupling capacitor The output is biased at VBB 2 referenced to GND With the resistor Rgals the gain of the loudspeaker amplifier channel can be adjusted from 10 to 35 dB The gain equals typically 27 8 dB with resistor Rgals 255 kQ A capacitor Cgals can be connected in parallel with Rgals to provide a low pass filter which ca
95. witch over timing adjustment pin Transmit signal envelope timing adjustment pin Total Harmonic Distortion Idle mode timing Transmit noise envelope timing adjustment pin Transmit signal envelope sensitivity adjustment pin Auxiliary transmit input Base microphone amplifier input Base microphone amplifier output Transmit mode 84 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer VBB Positive supply of TEA1099 VDD Microcontroller supply of TEA1099 Vdt Vdialtone Dial tone detector level Vin DC voltage between LN and GND VOL Volume adjustment pin Vref Stabilized reference voltage between LN and SLPE Vslpe DC voltage level between SLPE and LN Zir Input impedance of the receive amplifier of the TEA1099 Zbal Anti sidetone network a Gain control factor of the AGC 85 Philips Semiconductors TEA1099 Speech and Handsfree IC with Application Note auxiliary inputs output and analog multiplexer

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