PCM6260-Q1: how should we use it in DC Differential mode

Hello Chi,

For questions 1 and 2 I believe you would get a good explanation by reading pages 36-38 of the datasheet.

https://www.ti.com/lit/ds/symlink/pcm6260-q1.pdf?ts=1627316969364&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FPCM6260-Q1

As for question 3, in what mode do you want mic to be in?

Best,

Carson

Low Power Audio Applications

hi, Carson

      thanks for your help .

       we want the mic works in DC differential mode.  in the datasheet it should be have the R1 pull up resisistor on INP and pull down resistor on INN, but in  the following file    https://www.ti.com/lit/ug/sbau341b/sbau341b.pdf?ts=1627350091371&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FPCM6260-Q1%253FkeyMatch%253DPCM6260-Q1%2526tisearch%253Dsearch-everything%2526usecase%253DGPN    in page 7 and page 8 it seems that it do not need the pull up and pull down resistor at al.

best regards.

chi guizhang

Hey Chi,

So if you want to use in DC-coupled mode the resistors are not actually required for operation, they are more or less recommended to prevent the lines from floating if microphone disconnects.

This is assuming your mic will provide the needed DC offset required for the input of the device 5V or higher. With a required common mode difference of 3.4V to 5V for 2Vrms swing. This is what EVM assumes

Is that clear?

Best Regards,

Carson

hi, Carson

      what do you mean the mic will provide the DC offset? you mean we should use the mic which have external power supply? the mic we are using do not have the external power supply.

     we modify the register according to the following map

we modify it to 0x1c, but it will report errors as folloing

can you tell me how should we do now?

I will need to replicate the set-up on my board and debug from there.

Thanks for the patience

Carson

Hello Again,

I apologize there was a misunderstanding on my part before, I only recently took over this product. You will need to connect the 1kpull-up resistor to MICBIAS  and 1k pull-down in order to have the device operate in the high swing-mode you have it configured for.

So disregard datasheet for EVM and connect those jumpers and inform me if that works for you.

Best Wishes,

Carson

hi, Carson, 

     so you mean the EVM datasheet have some problem.  then even in DC couple and differential mode i should use the pull up and pull down resistor to accquire  the bias voltage?  i will try it.

   another question how should i calculate the pull up and pull down resistor value?  and what the influence to SNR? 

best

chi guizhang 

Hello,

Yes the EVM datasheet does seem to contradict itself, though this part model has only recently come under my portfolio and so there may be something implied I may not be realizing but regardless if your mic needs bias then it will need to be connected to micbias somehow.

resistor values should be half of your mic resistance as it goes over in datasheet of part not EVM one.

Also in part datasheet there are multiple graphs of THD+N that use MICBIAS to give you idea of SNR.

Let me know how this goes.

Best Regards,

Carson