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PCM5142: clock setting

KANJI SHIBATANI
Mastermind 6205 points

Part Number: PCM5142

My customer want to use PCM5142 for new design.

But would you please have your opinion?

Q1) 4 wire I2S input as "SCK=BCK" is OK for auto-configure the clock tree and PLL  ?

So, Table 32 on Data Sheet  page47  discribes the relationship between SCK and Sampling frequency (LRCK),

but  Customer will use as  following  case a),b) as SCK=BCK.

Customer says  it works correctly in PCM5142 EVM without PLL setting, but customer want to have your confirmation.

a)LRCK=352.80KHz SCK=BCK=22.5792MHz

b)LRCK=384.00KHz SCK=BCK=24.5760MHz

 

Q2) LRCK 256KHz 4-wire mode  on SCK=BCK=16.384MHz can be auto-configured?

This setting  seems such as " Not Common audio sample frequencies" and concern is customer must set PLL setting....

Do you think 4-wire auto-configure the clock tree and PLL available for LRCK=256KHz and SCK=BCK=16.384MHz?

Customer says  PCM5142 EVM works correctly with auto-configured in case LRCK=256KHz/SCK=BCK=16.384MHz.

How do you think? ( Its OK because multiple of 32KHz ?)

Best Regards

  • 0
    TI__Guru 57800 points

    Hi, Shibatani-san,

    Please refer to below comments:

    Q1- Correct, this device is able to operate in 3-wire PCM mode with BCLK being used as the clock source for the internal circuitry of the device instead of SCK. Please refer to Table 33 of the datasheet, there you can find the supported BCLK and LRCK clocks for this operation mode.

    Q2- Even if the device is able to operate properly at 256KHz sampling rate, we cannot guarantee that the performance of the PCM5142 will match the specs defined in the datasheet as this is not a recommended operation mode. As you mention, the part seems correctly auto-configure the clocks under 256KHz sample rate as it recognizes it is a multiple of a valid sampling rate. However, we don't recommend using this part with that sampling rate. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Mastermind 6205 points

    Dear Melendez san

     

    Thank you for your answer about quickly!! I am sorry my poor English.

    Please let me explain again about Q1.

     

    Customer want to use PCM5142 for software control(not H/W control)  without PLL setting  .... (PLL setting  is so complicated for customer).

    We know hardware mode 3-wire PCM in 8.3.6.3 in d/s , we can use 3-wired mode without PLL setting ( auto-confugure) , but they hope software mode.

     So, customer 's question( usage ) is about: 8.3.6.2 Clock Slave Mode With Master and System Clock (SCK) Input (4 Wire I2S)  without PLL setting.

    ~~~~~~~~~~~~~~~~~~~

    Data sheet 8.3.6.2

    >In the presence of a valid bit SCK, BCK and LRCK in software mode, the device will auto-configure the clock tree


    >and PLL to drive the miniDSP as required.

    ~~~~~~~~~~~~~~~~

    Please let me confirm again:

    Is data sheet page 47, we can see Table 32. System Master Clock Inputs for Audio Related Clocks which is relationship between LRCK and SCK.

    Can customer use SCK(pin #20 )=BCK(pin) #21 =24.7576MHz( 64fs) at fs=384KHz?

    As per Customer, it works correctly, but they hope your confirmation.

     

    Best Regards

     

     

     

     

     

     

     

  • 0 in reply to KANJI SHIBATANI
    TI__Guru 57800 points

    HI, Shibatani-san,

    Thanks for the detailed feedback. The operation mode described is correct, as long as the PCM5142 receives valid audio SCK, LRCK and BCK, the device will automatically configure the clock tree. In this case, BCK=SCK=64×Fs is supported when sampling rate is 384KHz. 

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Mastermind 6205 points

    Dear Melendez-san

    Thank you for your answer !

    Thank you again

     

     

  • 0 in reply to KANJI SHIBATANI
    Expert 1230 points
    Hi, Diego

    I have a question.

    Now I am designing dsp - PCM5142 connection.

    Actually I just connect BCK, DIN, LRCK for I2S communication. Do I need to connect SCK too? but DSP device doesn't have SCK pin.

    thanks
  • 0 in reply to minkyo seo
    TI__Guru 57800 points

    Hi, Minkyo, 

    The PCM5142 is able to operate in 3-wire mode (without SCK) by adjusting the input clocks to operate form BCK instead of SCK

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 1230 points
    Thank you for the answer.

    Actually, I'm going to use C5545 to program PCM5142 through I2C.

    and also I'm going to connect C5545 and PCM5142 with I2S.

    So, I can just connect BCK and LRCK, DIN, and it has no problem.

    Right?

    As always, Thank you for your support.
  • 0 in reply to minkyo seo
    TI__Guru 57800 points

    Hi, Minkyo, 

    Correct, you just need to make sure the clock registers of the device are properly configured to operate in 3-wire mode.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer

  • 0 in reply to Diego Melendez
    Expert 1230 points
    Thank you for the answer.

    It helps me a lot.
  • 0 in reply to minkyo seo
    Expert 1230 points
    Sorry Diego,

    May I have one more question?

    how can I control volume during runtime?

    Maybe, I have to modify volume register value.

    Is there some tips for that?

    Thank you.
  • 0 in reply to minkyo seo
    TI__Guru 57800 points

    Hi, Minkyo,

    You can change the volume of the device by using the Digital Volume Control registers, you only need to update the register of the required channel with the desired level and the device will adjust the volume of the audio signal. This register can be accessed while the device is running without any issue.

    Best Regards,

      -Diego Meléndez López
       Audio Applications Engineer