Si4831/35 AM/FM/SW TUNER
Contents
1. A Yes PVR tuning frequency stays stable at various conditions while PVC tuning frequency drifts Reliability test results proved the following e Testing platform Si4835 DEMO with R121 PVR and Sony clock radio ICF C218 with PVC e Tuned frequency is determined at maximum SINAD and S N point Tests Settings Si4831 35 PVR SONY ICF C218 PVC Room start 98 1 MHz 98 1 MHz Hot temp Humidity T 45 C H 80 98 1 MHz 98 14 MHz Room end 98 1 MHz 98 1 MHz Room start 98 1 MHz 98 1 MHz Cold T 10 C 98 1 MHz 98 17 MHz Room end 98 1 MHz 98 17 MHz Long term high temp humidity Room start 98 1 MHz 98 1 MHz T 60 C H 90 100 Hour Room end 98 1 MHz 98 28 MHz Short term high temp humidity Oman ARE MEZ Mn T 60 C H 80 6 Hour Room end 98 1 MHz 97 98 MHz Short term cold Room start 98 1 MHz 98 1 MHz T 25 C 6 Hour Room end 98 1 MHz 98 1 MHz Hot cold cycle test Room start 98 1 MHz 98 1 MHz T 70 C T 10 C 5 cycles Room end 98 1 MHz 98 06 MHz Rev 0 1 5 SILICON LABS Si4831 35 FAQ Q What do I need to change on the appearance of my existing model if using Si4831 35 Keyword s Existing model Device s Si4831 35 HW Rev s All A The traditional PVC frequency display is non linear however the Si4831 35 s advanced tuning algorithm makes the tuned frequency linear with the PVR turning angle so Si4831 35 offers more accuracy to estim2. SILICON LABS i4831 35 AM FM SW TUNER FREQUENTLY ASKED QUESTIONS Rev 0 1 4 11 Copyright 2011 by Silicon Laboratories Si4831 35 FAQ Rev 0 1 4 11 Copyright 2011 by Silicon Laboratories Si4831 35 FAQ i4831 35 FAQ SILICON LABS S 4831 35 AM FM SW TUNER FREQUENTLY ASKED QUESTIONS Table of Contents What s the advantage of using PVR tuning instead of PVC 0 000 eee 4 PVR tuning stable under different environmental conditions ullus 5 What do need to change on the appearance of my existing model if using Si4831 35 6 How is the tuning feel of PVR with Si4831 35 is it easy to tune exactly to a station 6 How is the frequency display accuracy of Si4831 35 PVR tuning compared with PVC tuning ex k d baba xS WE ecce ERES 6 Why are some of my Si4831 35 models occasionally unable to power up after quick power off on cycles l M 9 e e o o o o o e eee 7 Why is the measured SNR and Sensitivity often better when using an audio analyzer than when using a multimeter 9 If my application is mono audio how should use Si4831 35 2220 00 ee 9 When switching on the power supply there is a small but audible power on pop noise How can this pop noise be mitigated FM 01 1 9 Why is the narrow FM AFC range not a problem in the Si4831 35 10 How do minimize the frequency display position hysteresis with PVR tunin
3. as shown in Figure 7 to Lout and Rout of Si4831 35 respectively Rev 0 1 9 SILICON LABS Si4831 35 FAQ Figure 7 Power On Pop Noise Muting Circuit Q Why is the narrow FM AFC range not a problem in the Si4831 35 Keyword s AFC Range Traditional Analog FM tuner Selectivity Device s Si4831 35 HW Revis All A For traditional analog FM tuners the FM AFC range by standard measurement procedures is normally between 150 and 500 kHz but for Si4831 35 the tested AFC range is at 40 60 kHz based on the traditional test method The Si4831 35 has a digital architecture with an advanced tuning algorithm therefore it has dynamic AFC range When PVR is rotated during tuning Si4831 35 broadens its AFC range to around 500 kHz for easy station capturing and locking When tuning is stopped Si4831 35 automatically narrows its AFC range to 40 60 kHz for excellent selectivity performance Q How do I minimize the frequency display position hysteresis with PVR tuning Keyword s Position Hysteresis Frequency Display PVR tuning Device s Si4831 35 HW Rev s All A The position hysteresis of the frequency display is caused by PVR itself and or the mechanical structure of the frequency display method Si4831 35 itself has no frequency display hysteresis issue PVRs are normally used for volume control where hysteresis is not an issue Test results showed some PVRs have hysteresis angles up to 4 5 degrees Ask your PVR vendo
4. voltmeter is low cost and is widely used by many audio customers A typical voltmeter model is TVT 322 Using the audio analyzer the measured SNR and sensitivity is normally better than when using a voltmeter for the following reasons 1 The frequency bandwidth of an audio analyzer is narrower than a voltmeter s bandwidth Audio analyzer bandwidth is normally up to 22 kHz this is the real audio signal bandwidth For the voltmeter the frequency bandwidth is much wider and different models have different bandwidths normally above 200 kHz For the TVT 322 the bandwidth is up to 1 MHz Because of the wider frequency bandwidth the voltmeter always measures a higher noise level than the audio analyzer and therefore has a lower SNR value and Sensitivity value But for true audio measurement the noise level above 22 kHz should not be counted as it is beyond the human ear frequency audible range 2 The audio analyzer is a more advanced instrument than the voltmeter it can measure signal level and noise level at the same time and can directly calculate SNR data For the voltmeter SNR data can only be obtained by first turning on modulation to get the signal level then turning off modulation to get the noise level and then calculating SNR data as the delta So for the voltmeter the measured signal level and noise level do not occur at the same time hence it is not a ttue SNR measurement Q If my application is mono audio how should use Si
5. 4831 35 Keyword s Mono Audio Stereo Audio Device s Si4831 35 HW Rev s All A The Si4831 35 is a stereo audio tuner with two stereo thresholds 20 dBuV and 28 dBuV When the input RF level is below the selected stereo threshold the chip outputs mono audio When the input RF signal is above the selected stereo threshold it automatically outputs stereo audio The following measures are recommended for mono audio applications 1 Choose the wanted FM band with stereo indication threshold of 28 dBuV 2 Connect Lout and Rout together right after the AC coupling capacitors of 4 7 uF Q When switching on the power supply there is a small but audible power on pop noise How can this pop noise be mitigated Keyword s Pop noise Device s Si4831 35 HW Revis All A Compared with Si4830 34 A20 the Si4831 35 has greatly reduced the power on pop noise To further migrate the pop noise the following measures are recommended 1 The ac coupling capacitors in series with Lout and Rout of Si4831 35 must be no less than 4 7uF 2 Normally there is a large power supply filtering capacitor at the power supply of audio AMP put the capacitor as close to the power supply pin of audio AMP as possible and give this capacitor a large value so that at power up audio AMP starts up more slowly than Si4831 35 this will make the power on pop noise smaller 3 To completely remove the power on pop noise adding a transistor E cap muting circuit
6. ate the frequency from the analog display marking To use Si4831 35 for existing PVC models you only need to change the frequency marking and make it linear Traditional PVC non linear frequency display amp 103 l l N j 93 88 93 98 103 108 MHz 88 108 Si4831 35 PVR linear frequency display 88 93 98 103 108 MHz Figure 2 PVC PVR Frequency Display Q How is the tuning feel of PVR with Si4831 35 is it easy to tune exactly to a station Keyword s Tuning feel Device s Si4831 35 HW Rev s All A Compared with Si4830 34 A20 the Si4831 35 uses a new tuning algorithm that allows the user to hear one station across a larger frequency range At the same time the user can easily feel or tell if the tuned position is the best by the sound The new tuning algorithm was added to improve the tuning feel and has been well received in the marketplace The algorithm was carefully optimized such that selectivity was not compromised therefore weak station is still easy to tune Q How is the frequency display accuracy of Si4831 35 PVR tuning compared with PVC tuning Keyword s Frequency display accuracy Device s Si4831 35 HW Rev s All A Si4831 35 PVR tuning frequency display accuracy is not any worse than traditional analog radios The tuning position inaccuracy has most to do with the PVR itself but this is not unique to PVR PVC will also have some position inaccuracy Traditional PVC tuning analog radio has a much more seve
7. g 10 Rev 0 1 4 11 Copyright 2011 by Silicon Laboratories Si4831 35 FAQ Si4831 35 FAQ Q What s the advantage of using PVR tuning instead of PVC PVR PVC resistance ratio Keyword s Device s Si4831 35 HW Rev s All A PVR tuning has the following advantages compared with PVC tuning 1 Cost saving e Material cost PVR is 0 05 vs PVC for 0 12 for the same quantity and quality e Labor cost 2 Reliable life time and endurance test proven is better than PVC e Test Method 100 000 PVR full range rotations e SINAD SNR sensitivity at three frequency points remain unchanged before and after rotation test Before Test After Test FM Test Points MHz m S N dB an SE S N dB a 88 1 57 58 2 57 58 2 98 1 57 58 2 57 58 2 107 9 56 57 3 56 57 3 e PVR value and the frequency display mark stay within spec e After 10K times rotations PVR value stays the same frequency display alignment unchanged e After 100K times rotations PVR value changes less than10 no visible change to frequency display alignment This is because Si4831 35 uses resistance ratio not the absolute resistance value for tuning to ensure display accuracy Figure 1 PVR Resistance Ratio Rev 0 1 4 SILICON LABS Si4831 35 FAQ Q PVR tuning stable under different environmental conditions Keyword s PVR tuning environmental conditions Device s Si4831 35 HW Rev s All
8. perly and can t be powered up and go into normal working mode SRST 0 RST 30 Figure 3 Reset Pulse for Si4831 35 VCC Figure 4 RC Reset Circuit of Si4831 35 Rev 0 1 7 SILICON LABS Si4831 35 FAQ Figure 5 Vcc green and RST yellow Change During Power Off VOUT 1 VIN Q2 8050 R42 4k7 Optimized Cap value CONTROL Dischar ge resistor Figure 6 Typical Power Supply Circuit Figure 6 shows the typical power supply circuit of a tuner the solution to the power up issue is 1 Add a discharge resistor at the output of tuner power supply to speed up the discharge process when the power is off 2 Optimize the filtering caps capacity to a small value Si4831 35 consumes only around 20 mA current in normal working mode so the power supply circuits do not need to contain a large value of filtering caps normally no more than 47 uF is recommended 8 Rev 0 1 e SILICON LABS Si4831 35 FAQ Q Why is the measured SNR and Sensitivity often better when using an audio analyzer than when using a multimeter Keyword s Audio analyzer multimeter SNR Sensitivity Device s Si4831 35 HW Rev s All A Normally there are two kinds of instruments used for measuring SNR and Sensitivity one is a professional audio analyzer and another is a multimeter or voltmeter which can be a traditional needle display type or more modern digital display type The
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10. r to minimize the PVR position hysteresis Most of the existing mechanical structures for traditional analog radio frequency display method also fix the issue 10 Rev 0 1 SILICON LABS Si4831 35 FAQ NOTES SILICON LABS Rev 0 1 Si4831 35 FAQ CONTACT INFORMATION Silicon Laboratories Inc 400 West Cesar Chavez Austin TX 78701 Tel 1 512 416 8500 Fax 1 512 416 9669 Toll Free 1 877 444 3032 Please visit the Silicon Labs Technical Support web page https www silabs com support pages contacttechnicalsupport aspx and register to submit a technical support request Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice Silicon Laboratories assumes no responsibility for errors and omissions and disclaims responsibility for any consequences resulting from the use of information included herein Additionally Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters Silicon Laboratories reserves the right to make changes without further notice Silicon Laboratories makes no warranty rep resentation or guarantee regarding the suitability of its products for any particular
11. re tuned position drifting problem than Si4831 35 and for a longer term PVR tuning position accuracy of the Si4831 35 is better refer to the second question for more information 6 Rev 0 1 SILICON LABS Si4831 35 FAQ Q Why are some of my Si4831 35 models occasionally unable to power up after quick power off on cycles Keyword s Power off on cycles power up reset reset pulse Device s Si4831 35 HW Rev s All A Sometimes when the power switch is turned off on quickly or the power plug is plugged in out quickly the Si4831 35 can t be powered up properly and it can t go into normal working mode The reason for this is that during this type of fast power off on process the chip occasionally is not reset properly Si4831 35 is digital in nature an MCU and a DSP are integrated inside the chip To power up properly the chip needs a proper negative reset pulse during the quick power off on cycle As shown in Figure 3 the needed pulse width of tsnsr is several ms Because there are large filtering capacitors in the power supply circuit the dc supply voltage Vec to tuner is still present even though the main plug is disconnected and falls down slowly Accordingly the RST pin voltage falls down slowly so there is no needed reset pulse generated Figure 5 shows a typical Vec and RST voltage change curve during a power off on cycle In this case the RST voltage level doesn t drop below 0 3 Vac so the chip is not reset pro
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