Texas Instruments TPA3008D2 User's Manual
Contents
1. 37 24 Exposed Thermal 4 84 4 00 48 13 4 84 4 00 Top View NOTE linear dimensions are in millimeters Exposed Thermal Pad Dimensions 4206329 4 C 12 05 49 Texas PACKAGE OPTION ADDENDUM INSTRUMENTS www ti com 26 Mar 2007 PACKAGING INFORMATION Orderable Device Status Package Package Pins Package Eco Plan Lead Ball Finish MSL Peak Temp 9 Type Drawing Qty 008 2 ACTIVE HTQFP PHP 48 250 Green RoHS amp CU NIPDAU Level 4 260C 72 HR no Sb Br TPA3008D2PHPG4 ACTIVE HTQFP PHP 48 250 Green RoHS amp CU NIPDAU Level 4 260C 72 HR no Sb Br TPA3008D2PHPR ACTIVE HTQFP PHP 48 1000 Green RoHS amp NIPDAU Level 4 260C 72 HR no Sb Br TPA3008D2PHPRG4 ACTIVE HTQFP PHP 48 1000 Green RoHS amp NIPDAU Level 4 260C 72 HR no Sb Br 0 The marketing status values are defined as follows ACTIVE Product device recommended for new designs LIFEBUY TI has announced that the device will be discontinued and a lifetime buy period is in effect NRND Not recommended for new designs Device is in production to support existing customers but TI does not recommend using this part in a new design PREVIEW Device has b2. 37 24 Exposed Thermal 4 84 4 00 48 13 4 84 4 00 Top View NOTE linear dimensions are in millimeters Exposed Thermal Pad Dimensions 4206329 4 F 09 07 LAND PATTERN PHP R PDSO G48 PowerPAD Example Board Layout 0 127mm Thick Stencil Design Example Via pattern and copper pad size Reference table below for other may vary depending on layout constraints solder a Note 44x0 5 48x0 25 44x0 5 r 48x1 55 Non Solder Mask Defined Pad Example Solder Mask Opening Note F Pad Geometry 0 05 Note C All Around 4207626 4 B 03 06 NOTES linear dimensions are in millimeters B This drawing is subject to change without notice C Publication 7351 is recommended for alternate designs D This package is designed to be soldered to a thermal pad on the board Refer to Technical Brief PowerPad Thermally Enhanced Package Texas Instruments Literature No SLMAO02 SLMAO004 and also the Product Data Sheets for specific thermal information via requirements and recommended board layout These documents are available at www ti com http www ti com E Laser cutting apertures with
3. INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 TOTAL HARMONIC DISTORTION NOISE TOTAL HARMONIC DISTORTION NOISE vs vs FREQUENCY FREQUENCY 10 10 i 12 V D 18 V H RL 8Q a RL 8Q 5 Gain 21 6 dB 5 Gain 21 6 dB z z o 1 t 1 0 5 t 2 5 W 2 1 a a 2 o o E Po 1W s 01 041 1 9 2 5 o 3 z z 0 01 5 0 01 0 005 20 100 1k 10k 20k 20 100 1k 10k 20k f Frequency Hz f Frequency Hz Figure 3 Figure 4 TOTAL HARMONIC DISTORTION NOISE TOTAL HARMONIC DISTORTION NOISE vs vs OUTPUT POWER OUTPUT POWER 20 10 4 gl 068153 Vcc 18 V 1 RL 8 0 16 9 Gain 21 6 dB Gain 21 6 dB 2 2 2 2 5 1 1 5 2 9 a a o E 01 1 2 0 1 r 3 20 Hz 3 20 kHz un 3 E 8 001 0 01 E 20m 100 200 m 1 2 10 20 20m 100 m 200 m 1 2 10 20 Output Power W Output Power W Figure 5 Figure 6 49 5 INSTRUMENTS www ti com CLOSED LOOP RESPONSE 40 36 150 32 100 28 Gain 50 4 o a Phase 1 1 20 0 E 9 46 50 12 12 V 8 2890 100 Gain 32 dB 4 33 kHz RC LPF 150 0 10 100 1k 10k 80k Po Output Power W
4. tc gt n tc o a VCLAMPR Control B Right Differential Inputs E 0 47 uF 0 47 uF ah 7 Left Differential 9 0 2474 Inputs B 0 47 uF 0 47 uF Gain Control 2 Fault Reporting NC NC NC NC AGND AVDD COSC ROSC AGND VCLAMPL TPA3008D2 n o a 0 1 uF 0 1 uF 3 10 uF 10 uF 220 nF4 220 nF Chip ferrite bead example Fair Rite 251206700743 shown for EMI suppression 5 IN 71 nd PVCC 1 nF vae PVCC Figure 16 Stereo Class D With Differential Inputs 12 49 5 INSTRUMENTS www ti com AVCC 0 1 uF 10 uF 1 uF 220 120 L 1 uF 2085 R3 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 APPLICATION INFORMATION continued CLASS D OPERATION This section focuses on the class D operation of the TPA3008D2 Traditional Class D Modulation Scheme The traditional class D modulation scheme which is used
5. Frequency Hz Figure 7 OUTPUT POWER vs SUPPLY VOLTAGE THD N 1 _ Power represented by dashed line may require external heatsinking 9 10 11 12 13 14 Vcc Supply Voltage V Figure 9 Output Power W Efficiency 96 TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 OUTPUT POWER vs SUPPLY VOLTAGE 12 11 F RL 162 10 9 8 THD N 10 7 6 5 THD N 1 4 3 2 1 0 8 9 10 11 12 13 14 15 16 17 18 Vcc Supply Voltage V Figure 8 EFFICIENCY vs OUTPUT POWER 100 18 V 901 160 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10 Po Output Power Per Channel W Figure 10 TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 10 Efficiency Crosstalk dB EFFICIENCY TOTAL OUTPUT POWER 100 90 80 70 60 50 40 30 20 Vcc 12 V LCFilter 10 Resistive Load Stereo Operation 23 4 5 6 7 8 9 Total Output Power W 10 11 12 Figure 11 CROSSTALK vs FREQUENCY 12 V Po 2 5 W Gain 21 6 dB 8Q 20 100 1k f F
6. Signal The 3 dB frequency can be calculated using Equation 5 Use Table 1 for Z values f 1 2x 20 5 INPUT CAPACITOR C In the typical application an input capacitor C is required to allow the amplifier to bias the input signal to the proper dc level for optimum operation In this case C and the input impedance of the amplifier Z form a high pass filter with the corner frequency determined in Equation 6 3 dB fe 6 The value of C is important as it directly affects the bass low frequency performance of the circuit Consider the example where 7 is 137 and the specification calls for a flat bass response down to 20 Hz Equation is reconfigured as Equation 7 1 l 2 2 fo 7 In this example C is 58 nF so one would likely choose a value of 0 1 uF as this value is commonly used If the gain is known and is constant use 2 from Table 1 to calculate A further consideration for this capacitor is the leakage path from the input source through the input network Cj and the feedback network to the load This leakage current creates a dc offset voltage at the input to the amplifier that reduces useful headroom especially in high gain applications For this reason a low leakage tantalum or ceramic capacitor is the best choice When polarized capacitors are used the positive side of the capacitor should face the amplifier input in most applications as the dc level ther
7. the 200 family has a differential output where each output is 180 degrees out of phase and changes from ground to the supply voltage Vcc Therefore the differential prefiltered output varies between positive and negative where filtered 5096 duty cycle yields 0 V across the load The traditional class D modulation scheme with voltage and current waveforms is shown in Figure 17 Note that even at an average of 0 V across the load 50 duty cycle the current to the load is high causing high loss and thus causing a high supply current 412V Differential Voltage Across Load 12V Current mr Figure 17 Traditional Class D Modulation Scheme s Output Voltage and Current Waveforms Into an Inductive Load With No Input TPA3008D2 Modulation Scheme The 00802 uses a modulation scheme that still has each output switching from 0 to the supply voltage However OUTP and OUTN are now in phase with each other with no input The duty cycle of OUTP is greater than 5096 and OUTN is less than 5096 for positive output voltages The duty cycle of OUTP is less than 5096 and OUTN is greater than 5096 for negative output voltages The voltage across the load sits at 0 V throughout most of the switching period greatly reducing the switching current which reduces any I R losses in the load TPA3008D2 48 Texa 5 INSTRUMENTS www ti com SLOS435A MAY 2004 REV
8. 2 x As the output power increases the pulses widen making the ripple current larger Ripple current could be filtered with an LC filter for increased efficiency but for most applications the filter is not needed An LC filter with a cutoff frequency less than the class D switching frequency allows the switching current to flow through the filter instead of the load The filter has less resistance than the speaker which results in less power dissipation therefore increasing efficiency R3 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 APPLICATION INFORMATION continued Effects of Applying a Square Wave Into a Speaker Audio specialists have advised for years not to apply a square wave to speakers If the amplitude of the waveform is high enough and the frequency of the square wave is within the bandwidth of the speaker the square wave could cause the voice coil to jump out of the air gap and or scar the voice coil A 250 kHz switching frequency however does not significantly move the voice coil as the cone movement is proportional to 1 f for frequencies beyond the audio band Damage may occur if the voice coil cannot handle the additional heat generated from the high frequency switching current The amount of power dissipated in the speaker may be estimated by first considering the overall efficiency of the system If the on resistance rds on of the output transistors is considered to cause th
9. 2004 REVISED JULY 2004 FUNCTIONAL BLOCK DIAGRAM V2P5 VCLAMPR BSRN PVCCR 2 ROUTN 2 RINN PGNDR Gain EN AINE V2P5 PVCCR 2 i ROUTP 2 To Gain Adj PGNDR GAINO aan Blocks and ontro Start up Logic FAULT ROSC Ramp Detect Generator Biases Start up and COSC A and Protection VDD References Logic AVppREF AVCC PVCC TTL Input AGND 2 SHUTDOWN Buffer VClam VCC Compl ig VCLAMPL BSLN PVCCL 2 d LOUTN 2 LINN PGNDL BSLP LINP PVCCL 2 PGNDL Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 PHP PACKAGE TOP VIEW O gt 2 2 2 c U BSRP SHUTDOWN VCLAMPR RINN NC RINP NC V2P5 AVcc LINP NC LINN NC es TPA3008D2 AVpp GAINO COSC GAIN1 ROSC FAULT AGND NC VCLAMPL 00802 SLOS435A MAY 2004 REVISED JULY 2004 49 5 INSTRUMENTS www ti com TERMINAL FUNCTIONS PIN NAME PIN NUMBER yo DESCRIPTION AGND 26 30 Analog ground for digital analog cells in core 33 High voltage analog power supply not con
10. Continuous total power dissipation See Dissipation Rating Table Operating free air temperature range TA 40 to 85 Operating junction temperature range Ty 40 C to 150 C Storage temperature range Tig 65 to 150 Lead temperature 1 6 mm 1 16 inch from case for 10 seconds 260 1 Stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied Exposure to absolute maximum rated conditions for extended periods may affect device reliability DISSIPATION RATING TABLE DERATING PACKAGE Tas 25 FACTOR 70 85 1 9 4 3 W 1 14 C W 347 2 7 W 2 2 W 1 Based on a JEDEC high K PCB with the PowerPAD soldered to a thermal land on the printed circuit board See the PowerPAD Thermally Enhanced Package application note SLMA002 The PowerPAD must be soldered to the PCB RECOMMENDED OPERATING CONDITIONS T4 25 C unless otherwise noted MIN MAX UNIT Supply voltage 8 5 18 V High level input voltage SHUTDOWN GAINO GAIN1 2 V Low level input voltage Vi SHUTDOWN GAINO GAIN1 0 8 V SHUTDOWN V 18 V 10
11. GRAPHS FIGURE THD N Total harmonic distortion noise vs Frequency 1 2 3 4 THD N Total harmonic distortion noise vs Output power 5 6 Closed loop response 7 Output power vs Supply voltage 8 9 Efficiency vs Output power 10 Efficiency vs Total output power 11 Voc Supply current vs Total output power 12 Crosstalk vs Frequency 13 Supply ripple rejection ratio vs Frequency 14 CMRR Commom mode rejection ratio vs Frequency 15 TOTAL HARMONIC DISTORTION NOISE TOTAL HARMONIC DISTORTION NOISE vs vs FREQUENCY FREQUENCY 10 10 5 9 Vcc 18 V 12 V Ace 16 Q 2 L 2 Gain 21 6 dB Gain 21 6 dB z 4 5 2 5 E a a 9 E E Po lt 0 5 W E M I o1 S 2 5 W 3 Po 1W 9 z T a 1 a 001 Po lt 0 5 W 2 5 0 005 0 01 20 100 1k 10k 20k 20 100 Tk 10 20 f Frequency Hz f Frequency Hz Figure 1 Figure 2 TPA3008D2 48 Texas
12. High level input current GAINO V 5 5 V 18 1 SHUTDOWN V 0 V 18 V 1 Low level input current li GAINO GAIN1 V 5 5 V 18 1 High level output voltage FAULT 100 pA AVpp 0 8 V V Low level output voltage VoL FAULT lo 100 pA AGND 0 8 V V Frequency is set by selection of ROSC and COSC Oscillator frequency fosc see the Application Information Section 200 ae Operating free air temperature 40 85 49 5 INSTRUMENTS www ti com AVAILABLE OPTIONS TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 TA PACKAGED DEVICE 48 PIN HTQFP PHP 40 C to 85 TPA3008D2PHP 1 The PHP package is available taped and reeled To order a taped and reeled part add the suffix R to the part number e g TPA3008D2PHPR DC ELECTRICAL CHARACTERISTICS T4 25 C Voc 12 V R 8 Q unless otherwise noted PARAMETER TEST CONDITIONS MIN TYP MAX UNIT IVool Class D output offset voltage INN and INP connected together 2 5 55 mV 00 measured differentially Gain 31 8 dB V2P5 2 5 V Bias voltage No load 2 5 V 1 10 mA SHUTDOWN 2 V AVpp 5 internal supply voltage Vec 8 5 V to 18 V 4 5 5 5 5 V PSRR Power supply rejection ratio Voc 11 5 V to 12 5 V 76 dB loc Quiescent suppl
13. Important Information and Disclaimer The information provided on this page represents TI s knowledge and belief as of the date that it is provided TI bases its knowledge and belief on information provided by third parties and makes no representation or warranty as to the accuracy of such information Efforts are underway to better integrate information from third parties has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals and TI suppliers consider certain information to be proprietary and thus CAS numbers and other limited information may not be available for release In no event shall TI s liability arising out of such information exceed the total purchase price of the TI part s at issue in this document sold by TI to Customer on an annual basis Addendum Page 1 X3 Texas PACKAGE MATERIALS INFORMATION INSTRUMENTS www ti com 5 Oct 2007 TAPE AND REEL BOX INFORMATION REEL DIMENSIONS TAPE DIMENSIONS Cavity Dimension designed to accommodate the component width BO Dimension designed to accommodate the component length Dimension designed to accommodate the component thickness Overall width of the carrier tape Pitch between successive cavity centers Reel Width QUADRANT ASSIGNMENTS FOR PIN 1 ORIENTATION IN TAPE
14. Sprocket Holes 101 02 ai 02 1 4 i Q3 Q4 3 Q4 4 T Site Reel Diameter mm Device Package Pins TPA3008D2PHPR SITE 60 Pack Materials Page 1 X3 Texas PACKAGE MATERIALS INFORMATION INSTRUMENTS www ti com 5 Oct 2007 TAPE AND REEL BOX DIMENSIONS H gt a Device Package Pins Site Length mm Width mm Height mm TPA3008D2PHPR PHP 48 SITE 60 346 0 346 0 33 0 Pack Materials Page 2 MECHANICAL DATA PHP 5 048 PowerPAD PLASTIC QUAD FLATPACK Thermal Pad See Note D jeg Seating Plane ba 0 08 4146927 8 08 03 NOTES All linear dimensions are in millimeters B This drawing is subject to change without notice C Body dimensions do not include mold flash or protrusion D This package is designed to be soldered to a thermal pad on the board Refer to Technical Brief PowerPad Thermally Enhanced Package Texas Instruments Literature SLMA002 for information regarding recommended
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16. 49 5 NSTRUMENTS www ti com TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 10 W STEREO CLASS D AUDIO POWER AMPLIFIER FEATURES 10 W Channel Into an 16 0 Load From a 17 V Supply Up to 9296 Efficient Class D Operation Eliminates Need For Heatsinks 8 5 V to 18 V Single Supply Operation Four Selectable Fixed Gain Settings Differential Inputs Minimizes Common Mode Noise Space Saving Thermally Enhanced Packaging Thermal and Short Circuit Protection With Auto Recovery Option Pinout Similar to TPA3000D Family APPLICATIONS LCD Monitors and TVs All In One PCs DESCRIPTION The 00802 is a 10 W per channel efficient class D audio amplifier for driving bridged tied stereo speakers The TPA3008D2 can drive stereo speakers as low as 8 The high efficiency of the TPA3008D2 eliminates the need for external heatsinks when playing music The gain of the amplifier is controlled by two gain select pins The gain selections are 15 3 21 2 27 2 and 31 8 dB The outputs are fully protected against shorts to GND and output to output shorts fault ter minal allows short circuit fault reporting and automatic recovery Thermal protection ensures that the maxi mum junction temperature is not exceeded Shutdown Mute Control ROUTN PGNDR HJ 1 Right Differential Inputs lt Left Differential Inputs
17. 5 Gain 2 Control 3008D2 PVCCL PVCCL LOUTN Ir PGNDL CIT LOUTP PVCCL PVCCL PRODUCTION DATA information is current as of publication date Products conform to specifications per the terms of the Texas Instruments standard warranty Production processing does not necessarily include testing of all parameters TOptional output filter for EMI suppression Please be aware that an important notice concerning availability standard warranty and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet PowerPAD is a trademark of Texas Instruments Copyright O 2004 Texas Instruments Incorporated TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 ABSOLUTE MAXIMUM RATINGS over operating free air temperature range unless otherwise noted 0 49 5 INSTRUMENTS www ti com These devices have limited built in ESD protection The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates TPA3008D2 Supply voltage range 0 3 V to 20 V Load Impedance RL 260 SHUTDOWN 0 3 V to VCC 0 3 V Input voltage range V GAINO GAIN1 RINN RINP LINN LINP 0 3 V to 6 V
18. F capacitor was used instead and fc is 34 kHz which is above the desired value of 28 kHz C FILT 2x xf FILT 10 Table 3 Typical RC Measurement Filter Values MEASUREMENT Crit Efficiency 1000 Q 5 600 pF All other measurements 100 0 56 000 pF 23 Texas THERMAL PAD MECHANICAL DATA INSTRUMENTS www ti com PHP 5 048 HERMAL INFORMATION This PowerPAD package incorporates an exposed thermal pad that is designed to be attached directly to an external heatsink When the thermal pad is soldered directly to the printed circuit board PCB the PCB can be used as a heatsink addition through the use of thermal vias the thermal pad be attached directly to a ground or power plane whichever is applicable or alternatively a special heatsink structure designed into the PCB This design optimizes the heat transfer from the integrated circuit IC For additional information on the PowerPAD package and how to take advantage of its heat dissipating abilities refer to Technical Brief PowerPAD Thermally Enhanced Package Texas Instruments Literature o SLMAO02 and Application Brief PowerPAD Made Easy Texas Instruments Literature No SLMAOO4 Both documents are available at www ti com The exposed thermal pad dimensions for this package are shown in the following illustration 36 25
19. ISED JULY 2004 APPLICATION INFORMATION continued OUTP OUTN Differential 42y pp Voltage ov Load 12V Current TE OUTP L OUTN P Output 0 V Differential 412V Voltage ov Across Load 28523 Curent SSS SS SS SS SS SS SS SS SS SSS lt Figure 18 The TPA3008D2 Output Voltage and Current Waveforms Into an Inductive Load Efficiency LC Filter Required With the Traditional Class D Modulation Scheme The main reason that the traditional class D amplifier needs an output filter is that the switching waveform results in maximum current flow This causes more loss in the load which causes lower efficiency The ripple current is large for the traditional modulation scheme because the ripple current is proportional to voltage multiplied by the time at that voltage The differential voltage swing is 2 Vcc and the time at each voltage is half the period for the traditional modulation scheme An ideal LC filter is needed to store the ripple current from each half cycle for the next half cycle while any resistance causes power dissipation The speaker is both resistive and reactive whereas an LC filter is almost purely reactive The TPA3008D2 modulation scheme has little loss in the load without a filter because the pulses are short and the change in voltage is instead of
20. TL OUTPUT All of the class D APAs and many class AB APAs have differential inputs and bridge tied load BTL outputs Differential inputs have two input pins per channel and amplify the difference in voltage between the pins Differential inputs reduce the common mode noise and distortion of the input circuit BTL is a term commonly used in audio to describe differential outputs BTL outputs have two output pins providing voltages that are 180 degrees out of phase The load is connected between these pins This has the added benefits of quadrupling the output power to the load and eliminating a dc blocking capacitor A block diagram of the measurement circuit is shown in Figure 22 The differential input is a balanced input meaning the positive and negative pins have the same impedance to ground Similarly the BTL output equates to a balanced output 21 TPA3008D2 48 Texa S INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 Evaluation Module SERT quu q Low Pass Filter 4 Low Pass RC Filter Twisted Pair Wire Twisted Pair Wire Figure 22 Differential Input BTL Output Measurement Circuit The generator should have balanced outputs and the signal should be balanced for best results An unbalanced output can be used but it may create a ground loop that affects the measurement accuracy The analyzer must also have balanced inputs for the
21. Tl components To minimize the risks associated with customer products and applications customers should provide adequate design and operating safeguards TI does not warrant or represent that any license either express or implied is granted under any TI patent right copyright mask work right or other TI intellectual property right relating to any combination machine or process in which TI products or services are used Information published by TI regarding third party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof Use of such information may require a license from a third party under the patents or other intellectual property of the third party or a license from TI under the patents or other intellectual property of TI Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties conditions limitations and notices Reproduction of this information with alteration is an unfair and deceptive business practice TI is not responsible or liable for such altered documentation Information of third parties may be subject to additional restrictions Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and
22. board layout This document is available at www ti com lt http www ti com gt E Falls within JEDEC 5 026 PowerPAD is a trademark of Texas Instruments 48 5 INSTRUMENTS www ti com 48 5 THERMAL PAD MECHANICAL DATA INSTRUMENTS 5 048 Zu ERMAL INFORMA TION This PowerPAD package incorporates an exposed thermal pad that is designed to be attached directly to an external heatsink The thermal pad must be soldered directly to the printed circuit board PCB After soldering the PCB can be used as a heatsink In addition through the use of thermal vias the thermal pad can be attached directly to the appropriate copper plane shown in the electrical schematic for the device or alternatively can be attached to a special heatsink structure designed into the PCB This design optimizes the heat transfer from the integrated circuit IC For additional information on the PowerPAD package and how to take advantage of its heat dissipating abilities refer to Technical Brief PowerPAD Thermally Enhanced Package Texas Instruments Literature No SLMAQO2 and Application Brief PowerPAD Made Easy Texas Instruments Literature No SLMAOO4 Both documents are available at www ti com The exposed thermal pad dimensions for this package are shown in the following illustration 36 25
23. ctly A 220 nF ceramic capacitor rated for at least 25 V must be connected from each output to its corresponding bootstrap input Specifically one 220 nF capacitor must be connected from xOUTP to xBSP and one 220 nF capacitor must be connected from xOUTN to xBSN See the application circuit diagram in Figure 16 The bootstrap capacitors connected between the BSxx pins and corresponding output function as a floating power supply for the high side N channel power MOSFET gate drive circuitry During each high side switching cycle the bootstrap capacitors hold the gate to source voltage high enough to keep the high side MOSFETs turned on VCLAMP Capacitors To ensure that the maximum gate to source voltage for the NMOS output transistors is not exceeded two internal regulators clamp the gate voltage Two 1 pF capacitors must be connected from VCLAMPL pin 25 and VCLAMPR pin 36 to ground and must be rated for at least 25 V The voltages at the VCLAMP terminals vary with Vcc and may not be used for powering any other circuitry Internal Regulated 5 V Supply AVpp The AVpp terminal pin 29 is the output of an internally generated 5 V supply used for the oscillator preamplifier and volume control circuitry It requires a 1 uF capacitor placed close to the pin to keep the regulator stable This regulated voltage can be used to control GAINO and GAIN1 terminals but should not be used to drive external circuitry Differential Input T
24. d produces an analog signal output This amplifier circuit can be directly connected 10 the or other analyzer input This is not true of the class D amplifier system shown in Figure 21 b which requires low pass filters in most cases in order to measure the audio output waveforms This is because it takes an analog input signal and converts it into a pulse width modulated PWM output signal that is not accurately processed by some analyzers 20 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 Power Supply Signal Analyzer Generator 20 Hz 20 kHz 4 Basic Class AB Power Supply Low Pass RC Filter Signal cl D APA Generator R Low Pass Filter b Filter Free and Traditional Class D For efficiency measurements with filter free class D should be an inductive load like a speaker Figure 21 Audio Measurement Systems The TPA3008D2 uses a modulation scheme that does not require an output filter for operation but they do sometimes require an RC low pass filter when making measurements This is because some analyzer inputs cannot accurately process the rapidly changing square wave output and therefore record an extremely high level of distortion The RC low pass measurement filter is used to remove the modulated waveforms so the analyzer can measure the output sine wave DIFFERENTIAL INPUT AND B
25. e dominant loss in the system then the maximum theoretical efficiency for the TPA3008D2 with an 8 O load is as follows R L of 8 of 100 erig 009 86 8 T et 1 The maximum measured output power is approximately 8 5 W with an 12 V power supply The total theoretical power supplied P total for this worst case condition would therefore be as follows P _ Fo 85W total Efficiency 0 86 ROIN 2 Efficiency theoretical P The efficiency measured in the lab using an 8 Q speaker was 81 The power not accounted for as dissipated across the rps o may be calculated by simply subtracting the theoretical power from the measured power theoretical 10 49 9 88 0 61W Other losses total 3 total Measured 2 The quiescent supply current at 12 V is measured to be 22 mA It can be assumed that the quiescent current encapsulates all remaining losses in the device i e biasing and switching losses It may be assumed that any remaining power is dissipated in the speaker and is calculated as follows P dis 0 61 W 12 V x 22 mA 0 35 W 4 Note that these calculations are for the worst case condition of 8 5 W delivered to the speaker Because the 0 35 W is only 496 of the power delivered to the speaker it may be concluded that the amount of power actually dissipated in the speaker is relatively insignificant Furthermore this power dissipated is well within the specifications of mos
26. e is held at 2 5 V which is likely higher than the source dc level Note that it is important to confirm the capacitor polarity in the application For the best pop performance C should be less than or equal to 1uF Power Supply Decoupling Cs The 00802 is a high performance CMOS audio amplifier that requires adequate power supply decoupling to ensure that the output total harmonic distortion THD is as low as possible Power supply decoupling also prevents oscillations for long lead lengths between the amplifier and the speaker The optimum decoupling is achieved by using two capacitors of different types that target different types of noise on the power supply leads For higher frequency transients spikes or digital hash on the line a good low equivalent series resistance ESR ceramic capacitor typically 0 1 uF placed as close as possible to the device lead works best For filtering lower frequency noise signals a larger aluminum electrolytic capacitor of 10 uF or greater placed near the audio power amplifier is recommended The 10 capacitor also serves as local storage capacitor for supplying current during large signal transients on the amplifier outputs TPA3008D2 48 Texa S INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 BSN and BSP Capacitors The full H bridge output stages use only NMOS transistors Therefore they require bootstrap capacitors for the high side of each output to turn on corre
27. e set above fmax the highest frequency of the measurement bandwidth to avoid attenuating the audio signal Equation 9 provides this cutoff frequency fc The value of Rpt must be chosen large enough to minimize current that is shunted from the load yet small enough to minimize the attenuation of the analyzer input voltage through the voltage divider formed by and Rana rule of thumb is that Ret should be small 100 for most measurements This reduces the measurement error to less than 196 for RANA 2 10 ko RANA Rana EE E 8 12 fmax 9 An exception occurs with the efficiency measurements where must be increased by a factor of ten to reduce the current shunted through the filter must be decreased by a factor of ten to maintain the same cutoff frequency See Table 3 for the recommended filter component values Once fc is determined and is selected the filter capacitance is calculated using Equation 9 When the calculated value is not available it is better to choose a smaller capacitance value to keep fc above the minimum desired value calculated in Equation 10 1 R Table shows recommended values of Rgj 4 and based on common component values The value of fc was originally calculated to be 28 kHz for an fmax of 20 KHz however was calculated to be 57 000 pF but the nearest values of 56 000 pF and 51 000 pF were not available A 47 000 p
28. een announced but is not in production Samples may or may not be available OBSOLETE TI has discontinued the production of the device 2 Eco Plan The planned eco friendly classification Pb Free RoHS Pb Free RoHS Exempt or Green RoHS amp no Sb Br please check http Awww ti com productcontent for the latest availability information and additional product content details TBD The Pb Free Green conversion plan has not been defined Pb Free RoHS 5 terms Lead Free or Pb Free mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances including the requirement that lead not exceed 0 196 by weight in homogeneous materials Where designed to be soldered at high temperatures TI Pb Free products are suitable for use in specified lead free processes Pb Free RoHS Exempt This component has a RoHS exemption for either 1 lead based flip chip solder bumps used between the die and package or 2 lead based die adhesive used between the die and leadframe The component is otherwise considered Pb Free RoHS compatible as defined above Green RoHS amp no Sb Br TI defines Green to mean Pb Free RoHS compatible and free of Bromine Br and Antimony Sb based flame retardants Br or Sb do not exceed 0 196 by weight in homogeneous material 3 MSL Peak Temp The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications and peak solder temperature
29. he differential input stage of the amplifier cancels any noise that appears on both input lines of the channel To use the TPA3008D2 with a differential source connect the positive lead of the audio source to the INP input and the negative lead from the audio source to the INN input To use the TPA3008D2 with a single ended source ac ground the INP or INN input through a capacitor equal in value to the input capacitor on INN or INP and apply the audio source to either input In a single ended input application the unused input should be ac grounded at the audio source instead of at the device input for best noise performance SHUTDOWN OPERATION The TPA3008D2 employs a shutdown mode of operation designed to reduce supply current lcc to the absolute minimum level during periods of nonuse for power conservation The SHUTDOWN input terminal should be held high see specification table for trip point during normal operation when the amplifier is in use Pulling SHUTDOWN low causes the outputs to mute and the amplifier to enter a low current state Never leave SHUTDOWN unconnected because amplifier operation would be unpredictable For the best power off pop performance place the amplifier in the shutdown mode prior to removing the power supply voltage USING LOW ESR CAPACITORS Low ESR capacitors are recommended throughout this application section A real as opposed to ideal capacitor can be modeled simply as a resistor in series with an ideal ca
30. ible impact on measurement accuracy because it is well above the audible frequency range and the speaker cone cannot respond at such a fast rate The RC filter is not required when an LC low pass filter is used such as with the class D APAs that employ the traditional modulation scheme 200 TPA005Dxx The component values of the RC filter are selected using the equivalent output circuit as shown in Figure 23 RL is the load impedance that the APA is driving for the test The analyzer input impedance specifications should be available and substituted for Rana and Cana The filter components and can then be derived for the system The filter should be grounded to the APA near the output ground pins or at the power supply ground pin to minimize ground loops 22 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 Led RCLowPessFiters EXE it a AP Analyzer Input 1 n NAV I Cana T Ran R MW e Cana GND 2 11 22 32 521 EE ET ESE E J Figure 23 Measurement Low Pass Filter Derivation Circuit Class D APAs The transfer function for this circuit is shown in Equation 8 where ReqCeq Reg Ret Rana and Cana The filter frequency should b
31. nally connected to pins 14 and 15 not PVCCR 38 39 G internally connected to pins 46 and 47 PVCCR 46 47 internally connected to pins 38 and 39 RINP 3 Positive audio input for right channel RINN 2 Negative audio input for right channel ROSC 27 y o current setting resistor for ramp generator ROUTN 44 45 Class D 1 2 H bridge negative output for right channel ROUTP 40 41 Class D 1 2 H bridge positive output for right channel SHUTDOWN 1 Vieni rad IC low shutdown high operational TTL logic levels with VCLAMPL 25 Internally generated voltage supply for left channel bootstrap capacitors VCLAMPR 36 Internally generated voltage supply for right channel bootstrap capacitors V2P5 4 2 5 V Reference for analog cells Thermal Pad 1 Connect to AGND PGND should be the center point for both grounds Internal resistive connection to AGND 33 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 TYPICAL CHARACTERISTICS TABLE OF
32. nected internally to PVCCR or PVCCL AVpp 29 5 V Regulated output for use by internal cells and GAINO pins only Not specified for driving other external circuitry AVppREF 7 5 V Reference output connect to gain setting resistor or directly to GAINO BSLN 13 Bootstrap 1 for left channel negative high side FET BSLP 24 2 Bootstrap for left channel positive high side FET BSRN 48 Bootstrap 1 for right channel negative high side FET BSRP 37 Bootstrap 1 for right channel positive high side FET COSC 28 y o 1 for charge discharging currents onto capacitor for ramp generator Short circuit detect fault output 2727 Status is reset when power is cycled SHUTDOWN is cycled GAINO 9 Gain select least significant bit TTL logic levels with compliance to AVpp GAIN1 10 Gain select most significant bit TTL logic levels with compliance to AVpp LINN 6 Negative audio input for left channel LINP 5 Positive audio input for left channel LOUTN 16 17 Class D 1 2 H bridge negative output for left channel LOUTP 20 21 Class D 1 2 H bridge positive output for left channel NC 8 d 32 2 No internal connection PGNDL 18 19 2 Power ground for left channel H bridge PGNDR 42 43 Power ground for right channel H bridge PVCCL 14 15 _ Power supply for left channel H bridge internally connected to pins 22 and 23 not connected to PVCCR or PVCCL 22 23 _ bridge inter
33. owerPAD e Output filter The ferrite EMI filter Figure 20 should be placed as close to the output terminals as possible for the best EMI performance The LC filter Figure 19 should be placed close to the outputs The capacitors used in both the ferrite and LC filters should be grounded to power ground If both filters are used the LC filter should be placed first following the outputs e PowerPAD The PowerPAD must be soldered to the PCB for proper thermal performance and optimal reliability The dimensions of the PowerPAD thermal land should be 5 mm by 5 mm 197 mils by 197 mils The PowerPAD size measures 4 55 x 4 55 mm Four rows of solid vias four vias per row 0 3302 mm or 13 mils diameter should be equally spaced underneath the thermal land The vias should connect to a solid copper plane either on an internal layer or on the bottom layer of the PCB The vias must be solid vias not thermal relief or webbed vias For additional information see the PowerPAD Thermally Enhanced Package application note SLMAO02 For an example layout see the TPA3008D2 Evaluation Module TPA3008D2bEVM User Manual 5100165 Both the EVM user manual and the PowerPAD application note are available on the TI Web site at http www ti com TPA3008D2 48 Tex S INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 BASIC MEASUREMENT SYSTEM This application note focuses on methods that use the basic equipment listed below e Audio anal
34. p Bead Filter Chip bead example Fair Rite 2512067007Y3 Gain setting via GAINO and GAIN1 inputs The gain of the TPA3008D2 is set by two input terminals GAINO and GAIN1 The gains listed in Table 1 are realized by changing the taps on the input resistors inside the amplifier This causes the input impedance 2 to be dependent on the setting The actual gain settings are controlled by ratios of resistors so the gain variation from part to part is small However the input impedance may shift by 2096 due to shifts in the actual resistance of the input resistors For design purposes the input network discussed in the next section should be designed assuming an input impedance of 26 which is the absolute minimum input impedance of the TPA3008D2 At the lower gain settings the input impedance could increase as high as 165 Table 1 Gain Setting AMPLIFIER GAIN dB NPUT IMPEDANCE GAIN1 GAINO 0 0 15 3 137 0 1 212 88 1 0 27 2 52 1 1 31 8 33 INPUT RESISTANCE Each gain setting is achieved by varying the input resistance of the amplifier that can range from its smallest value 33 to the largest value 137 As a result if a single capacitor is used in the input high pass filter the 3 dB or cutoff frequency changes when changing gain steps Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 2 Input IN
35. pacitor The voltage drop across this resistor minimizes the beneficial effects of the capacitor in the circuit The lower the equivalent value of this resistance the more the real capacitor behaves like an ideal capacitor R3 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 SHORT CIRCUIT PROTECTION AND AUTOMATIC RECOVERY FEATURE The TPA3008D2 has short circuit protection circuitry on the outputs that prevents damage to the device during output to output shorts output to GND shorts and output to Vcc shorts When a short circuit is detected on the outputs the part immediately disables the output drive This is a latched fault and must be reset by cycling the voltage on the SHUTDOWN pin to a logic low and back to the logic high state for normal operation This clears the short circuit flag and allows for normal operation if the short was removed If the short was not removed the protection circuitry again activates The fault terminal can be used for automatic recovery from a short circuit event or used to monitor the status with an external GPIO THERMAL PROTECTION Thermal protection on the TPA3008D2 prevents damage to the device when the internal die temperature exceeds 150 C There is a 15 degree tolerance on this trip point from device to device Once the die temperature exceeds the thermal set point the device enters into the shutdown state and the outputs are disabled This is not a latched fault The
36. rements in connection with such use TI products are neither designed nor intended for use in automotive applications or environments unless the specific products are designated by TI as compliant with ISO TS 16949 requirements Buyers acknowledge and agree that if they use any non designated products in automotive applications TI will not be responsible for any failure to meet such requirements Following are URLs where you can obtain information on other Texas Instruments products and application solutions Products Applications Amplifiers amplifier ti com Audio www ti com audio Data Converters dataconverter ti com Automotive www ti com automotive DSP dsp ti com Broadband www ti com broadband Interface interface ti com Digital Control www ti com digitalcontrol Logic logic ti com Military www ti com military Power Mgmt power ti com Optical Networking www ti com opticalnetwork Microcontrollers microcontroller ti com Security www ti com security RFID www ti rfid com Telephony www ti com telephony Low Power www ti com lpw Video amp Imaging www ti com video Wireless Wireless www ti com wireless Mailing Address Texas Instruments Post Office Box 655303 Dallas Texas 75265 Copyright 2007 Texas Instruments Incorporated
37. requency Hz 10k 20k Figure 13 Supply Ripple Rejection Ratio dB 49 5 INSTRUMENTS www ti com SUPPLY CURRENT VS TOTAL OUTPUT POWER 2 0 LC Filter 1 8 Resistive Load Stereo Operation 1 6 lt Vcc 12 V 414 8 g 5 1 2 8 Vec 12 V 1 2 R 162 a 5 a 0 8 o 0 6 18 V 16 Q 0 4 0 2 0 0 2 4 6 8 10 12 14 16 18 20 Total Output Power W Figure 12 SUPPLY RIPPLE REJECTION RATIO vs FREQUENCY 0 10 Vcc 12 V V RIPPLE 200 mVpp 20 RL 8Q Gain 15 6 dB 30 40 50 60 70 80 90 100 2 100 1k 10k 20k f Frequency Hz Figure 14 Texas TPA3008D2 INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 COMMON MODE REJECTION RATIO vs FREQUENCY Vcc 12 V Gain 15 6 dB 289 Output Referred CMRR Common Mode Rejection Ratio dB 20 100 1k 10k 20k f Frequency Hz Figure 15 TPA3008D2 SLOS435A MAY 2004 REVISED JULY 2004 Shutdown Mute APPLICATION INFORMATION E 1 2 22 1 220 nF 4 tour 10 uF L N
38. system to be fully balanced thereby cancelling out any common mode noise in the circuit and providing the most accurate measurement The following general rules should be followed when connecting to APAs with differential inputs and BTL outputs e Use a balanced source to supply the input signal e Use an analyzer with balanced inputs Use twisted pair wire for all connections e Use shielding when the system environment is noisy e Ensure that the cables from the power supply to the APA and from the APA to the load can handle the large currents see Table 2 Table 2 shows the recommended wire size for the power supply and load cables of the APA system The real concern is the dc or ac power loss that occurs as the current flows through the cable These recommendations are based on 12 inch long wire with a 20 kHz sine wave signal at 25 C Table 2 Recommended Minimum Wire Size for Power Cables l DC POWER L AC POWER L Pour W 0 AWG Size oss MU oS 10 4 18 22 16 40 18 42 2 4 18 22 3 2 8 3 7 8 5 1 8 22 28 2 8 2 1 8 1 0 75 8 22 28 15 6 1 1 6 6 2 CLASS D RC LOW PASS FILTER An RC filter is used to reduce the square wave output when the analyzer inputs cannot process the pulse width modulated class D output waveform This filter has little effect on the measurement accuracy because the cutoff frequency is set above the audio band The high frequency of the square wave has neglig
39. t loudspeaker drivers in a system as the power rating is typically selected to handle the power generated from a clipping waveform When to Use an Output Filter for EMI Suppression Design the TPA3008D2 without the filter if the traces from amplifier to speaker are short lt 50 cm Powered speakers where the speaker is in the same enclosure as the amplifier is a typical application for class D without a filter Most applications require a ferrite bead filter The ferrite filter reduces EMI around 1 MHz and higher FCC and CE only test radiated emissions greater than 30 MHz When selecting a ferrite bead choose one with high impedance at high frequencies but low impedance at low frequencies Use a LC output filter if there are low frequency 1 MHz EMI sensitive circuits and or there are long wires from the amplifier to the speaker When both an LC filter and a ferrite bead filter are used the LC filter should be placed as close as possible to the IC followed by the ferrite bead filter TPA3008D2 9 TEXAS INSTRUMENTS www ti com SLOS435A MAY 2004 REVISED JULY 2004 APPLICATION INFORMATION continued 33 uH OUTP e 9 gt Ly ELS 0 1 uF 1 0 47 uF 33 uH OUTN e 9 Lo 0 1 Figure 19 Typical LC Output Filter Cutoff Frequency of 27 kHz Speaker Impedance 8 Q Ferrite Chip Bead 1nF Ferrite Chip Bead OUTP Figure 20 Typical Ferrite Chi
40. thermal fault is cleared once the temperature of the die is reduced by 20 C The device begins normal operation at this point with no external system interaction PRINTED CIRCUIT BOARD PCB LAYOUT Because the TPA3008D2 is a class D amplifier that switches at a high frequency the layout of the printed circuit board PCB should be optimized according to the following guidelines for the best possible performance Decoupling capacitors The high frequency 0 1 decoupling capacitors should be placed as close to the pins 14 15 22 23 38 39 46 and 47 and pin 33 terminals as possible The V2P5 pin 4 capacitor AVpp pin 29 capacitor and VCLAMP pins 25 and 36 capacitor should also be placed as close to the device as possible Large 10 uF or greater bulk power supply decoupling capacitors should be placed near the TPA3008D2 on the PVCCL PVCCR and terminals Grounding The pin 33 decoupling capacitor AVpp pin 29 capacitor V2P5 pin 4 capacitor COSC pin 28 capacitor and ROSC pin 27 resistor should each be grounded to analog ground AGND pins 26 and 30 The PVCC decoupling capacitors should each be grounded to power ground PGND pins 18 19 42 and 43 Analog ground and power ground may be connected at the PowerPAD which should be used as a central ground connection or star ground for the TPA3008D2 Basically an island should be created with a single connection to PGND at the P
41. trapezoidal walls and also rounding corners will offer better paste release Customers should contact their board assembly site for stencil design recommendations Refer to IPC 7525 for stencil design considerations F Customers should contact their board fabrication site for recommended solder mask tolerances and tenting options for vias placed in the thermal pad 35 TEXAS INSTRUMENTS www ti com IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries TI reserve the right to make corrections modifications enhancements improvements and other changes to its products and services at any time and to discontinue any product or service without notice Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete All products are sold subject to Tl s terms and conditions of sale supplied at the time of order acknowledgment TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with standard warranty Testing and other quality control techniques are used to the extent deems necessary to support this warranty Except where mandated by government requirements testing of all parameters of each product is not necessarily performed TI assumes no liability for applications assistance or customer product design Customers are responsible for their products and applications using
42. y current SHUTDOWN 2 V no load 11 22 mA Quiescent supply current in shut a 80 down mode SHUTDOWN 0 V 1 6 25 Vcc 12V High side 600 DS on Drain source on state resistance 10 1 Low side 500 Total 1100 1300 GAINO 0 8 V 14 6 15 3 16 2 0 8 V GAINO 2 20 5 21 2 21 8 G Gain dB GAINO 0 8 V 26 4 27 2 27 8 GAIN1 2V 2 31 1 31 8 32 5 ton Turnon time 1 uF SHUTDOWN 2 16 ms tort Turnoff time Civaps 1 SHUTDOWN 0 8 V 60 us AC ELECTRICAL CHARACTERISTICS T4 25 Voc 12 V R 8 unless otherwise noted PARAMETER TEST CONDITIONS MIN TYP MAX UNIT 200 MVpp ripple from 20 Hz to 1 kHz Supply voltage rejection ratio Gain 15 6 dB Inputs ac coupled to GND 70 BB THD N 0 13 1 kHz 8 Q 5 THD N 10 f 1 kHz R 8 8 5 Continuous output power THD N 0 16 f 1 kHz 16 Q 5 Vcc 217 V THD N 10 f 1 kHz 16 Q 10 Vcc 217 V THD N Hs harmonic distortion plus Po 1W f 1kHz R 82 0 1 20 Hz to 22 kHz A weighted filter _ Output integrated noise floor Gain 15 6 dB 80 dB Crosstalk Po 1 W R 8 Gain 15 6 dB 93 dB 1 kHz Maximum output at 0 595 SNR Signal to noise ratio f 1 kHz Gain 15 6 dB 97 dB Thermal trip point 150 Thermal hystersis 20 49 5 INSTRUMENTS www ti com TPA3008D2 SLOS435A MAY
43. yzer or spectrum analyzer e Digital multimeter DMM e Oscilloscope Twisted pair wires e Signal generator e Power resistor s e Linear regulated power supply e Filter components EVM or other complete audio circuit Figure 21 shows the block diagrams of basic measurement systems for class AB and class D amplifiers A sine wave is normally used as the input signal because it consists of the fundamental frequency only no other harmonics are present An analyzer is then connected to the APA output to measure the voltage output The analyzer must be capable of measuring the entire audio bandwidth A regulated dc power supply is used to reduce the noise and distortion injected into the APA through the power pins A System Two audio measurement system AP II Reference 1 by Audio Precision includes the signal generator and analyzer in one package The generator output and amplifier input must be ac coupled However the EVMs already have the ac coupling capacitors so no additional coupling is required The generator output impedance should be low to avoid attenuating the test signal and is important because the input resistance of APAs is not high Conversely the analyzer input impedance should be high The output impedance of the APA is normally in the hundreds of milliohms and can be ignored for all but the power related calculations Figure 21 a shows a class AB amplifier system It takes an analog signal input an
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