TLV320AIC3254: DC offset in ADC data

user4451570

Prodigy 180 points

Part Number: TLV320AIC3254
Other Parts Discussed in Thread: CC3200

I have designed custom bluetooth board using TLV320AIC3254.

I found there is DC offset in ADC data(MIC input) around -585 as attached file below.

It should be around 0.

I understand , to remove DC offset, I need to use high pass filter.

But I do not know how to implement high pass filter on TLV320AIC3254,

because there is no document or no source code(script) about that.

Could you tell me how to implement that?

Best regards,

over 1 year ago

0 Jeff McPherson over 1 year ago

TI__Mastermind 23155 points

Hi,

Today is a TI Holiday and our experts are out of office. Please give us another day to look at and answer your question. For record keeping purposes please do not reply to this message unless 48 hours have passed without a response.

Thank you for your patience,

Jeff

0 Jeff McPherson over 1 year ago in reply to Jeff McPherson

TI__Mastermind 23155 points

Hi,

Can you clarify, this DC offset is measured on the input pins directly? What is the units on your graph? AC coupling the signal with a 1uF or so should remove unnecessary DC offset.

Best regards,

Jeff

0 user4451570 over 1 year ago in reply to Jeff McPherson

Prodigy 180 points

Hi,

Thank you for replying.

DC offset of the graph is I2S digital data value.

And I have already put 1uF series capacitor at ADC input as reference design of CC3200 AUDIO Boosterpack.

So I think ADC module has DC offset somewhere inside.

brest regards,

+1 Jeff McPherson over 1 year ago in reply to user4451570

TI__Mastermind 23155 points

Hi,

The reference guide gives more information than the datasheet on how to program the coefficients (IIR and Biquads) of the ADC processing block: https://www.ti.com/lit/an/slaa408a/slaa408a.pdf?ts=1657035177120.

Since this part has a miniDSP on it, you could also use PurePath Studio to implement some simple high pass filtering and see if that helps. https://www.ti.com/tool/AICPUREPATH_STUDIO

Best regards,

Jeff

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TLV320AIC3254: DC offset in ADC data