Part Number: TLV320AIC3268
According to AIC3268 datasheet, the max input level is 0.5Vrms per input. For differential input, it is up to 1Vrms.
If I want to handle the differential signal with +4dBu level (professional line level, comes from audio mixer, microphone preamp...etc).
+4dBu is about 1.228Vrms so the divider network is necessary!
I am new to audio hardware circuit design. Please help me check:
(1) Use the divider network to half the differential input voltage, enlarge the maximum voltage to 2Vrms.
In Figure 111. Analog Input Connection With Resistor Divider Network of datasheet, R1 || R2 << Req
Could you suggest me the resistor value R1, R2 of the divider?
(2) Is it any risk for divider to handle +4dBu signal for long time? The audio quality is OK?
(3) BTW, use the 1 Vrms as our differential input maximum voltage and limit audio source output(use audio mixer gain control to lower audio etc.) or use the divider up to 2Vrms. which is better?
I think lower the audio source gain may decrease the SNR in audio mixer and cause the bad quality. Could you give some suggestions?
The TLV320AIC3268 is an audio codec targeted for portable applications, so the compatibility with professional line level is not supported directly and signal conditioning is required. The input conditioning can be achieved with a resistor divider network as mentioned in section 18.104.22.168 of the datasheet, but for the output signal conditioning, an external amplifier/line driver will be required.
The selection of the resistor network depends on the PGA and Rin settings, I can help recommending the values but will need that information first. The following formulas are used for the R1 and R2 calculation:
-Diego Meléndez López Audio Applications Engineer
In reply to Diego Melendez:
In reply to Steven Weng1:
Sorry, I didn't noticed the image was corrupt. Please refer to below:
If differential configuration is used, you will need only the value of RIN for the calculation of the required attenuation network. You should be able to change the gain without issues with this configuration.
Sorry for the issues, I don't know why the image is corrupt. Correct, the formulas are the same of section 22.214.171.124. For differential mode inputs, Rin=Req and the gain does not affect the calculation. So, the only consideration for the R1 and R2 selection would be as follows:
Req=RinR1 || R2 << ReqR1 || R2 << RinR1 || R2 << 20KΩ
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