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TLV320ADC3101-Q1: digital mic interface

Shinji Tsuji
Genius 12808 points
Part Number: TLV320ADC3101-Q1
Other Parts Discussed in Thread: TLV320ADC3101

Hi team,

I want to utilize digital microphone input of this device and setup using TLV320ADC3101EVM with digital microphone.

I sent BCLK(3.072MHz) to TLV320ADC3101 BCLK input and set internal clock divider and multiplexer to send 3.072MHz clock from DMCLK,

then I got PDM Data from digital microphone successfully.

But DOUT from TLV320ADC3101 is also PDM data.

Is there something wrong with my setting?

1. MCLK is left open. Is MCLK required for this use case?

2. Could you advise the register 81 setting?

Should I set it like 00001100?

I would like to know if D3/D2 need to be 1?

regards,

  • 0
    TI__Mastermind 30090 points

    Hello Shinji, 

    1. MCLK is not required.  if not being used you can connect the MCLK pin to GND. 

    2. register 81 should be 11001100.  (digital mics enabled for ADC channels, and ADCs powered up)

    I have never seen the DOUT transmit PDM data, and would not expect to see that behavior. make sure register 81 is set to 11001100 and check again.

    best regards,

    -Steve Wilson

  • 0 in reply to Steve-Wilson
    TI__Genius 12808 points

    Hi Steve,

    Thank you for your prompt reply.

    I found this behavior (PDM output from DOUT) while configuring the GUI of EVM.

    I changed the "DOUT Output Source" in Audio Interface tab of the GUI, then the data source seems changed.

    When I overlay the cursor, it shows "p0_r33_d1" which is reserved in the datasheet.

    Is there a reserved mode to output PDM data?

    Which item should I select this "DOUT Output Source" window?

    ADC setting

    When using digital microphone, I thought ADC can be powered down and then all the ADC related register should be don't care, correct?

    Is there any ADC related registers (such as ADC_CLK) needed to be configured?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Mastermind 30090 points

    Shinji, 

    Interesting.  If you compare the register maps of the ADC3101, AIC36 and AIC3254 you see a lot of similarities, this is because these devices were developed around the same time and share a lot of the same internal blocks.  The EVM GUIs also share the same software core. 

    Regarding the PDM output you are seeing,  what I suspect is that this the secondary DIN (from the AIC devices) was repurposed for the digital microphone interface of the ADC3101.  So what you are seeing is simply the PDM input sent back out SDOUT.  this is of course not very useful and that is why the register is reserved.  However the GUI should have hidden that control. 

    regarding ADC registers,  The digital microphones still use then ADC processing (decimation filters, biquads filters, custom PPS process flow) When you "enable" the digital mic inputs, this doesn't power up the ADC processing,  it simply tells the device that the delta-sigma modulator doesn't need to be powered up.  powering up the ADC then enables the ADC processing for the Digital mic inputs. 

    ADC_CLK is necessary to run the DSP and provide a source for ADC_MOD_CLK which is used as the clock for your DMIC. 

    best regards,

    -Steve Wilson