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PCM1795 SNR

KANJI SHIBATANI
Mastermind 6205 points

Other Parts Discussed in Thread: PCM1795


Hello

This is the issue about SNR of PCM1795 in customer's  System ( including op amp) .

D.range  of PCM1795 seems different  between prevous fs.

If previous fs= 192kHz, then chagne to 96kHz, D.Range is 114dB. If previous fs=48KHz, then chnage to 96KHz,D.Range=111dB.

As a result,  there are 3dB difference depend on previous fs...

Do you have a idea to solve this?

Here is the details.....

--------------------------------

** Conditions:

Input：PCM/24bit  I2S

SCK=24.576MHz    BCK=64fs  LRCK=1fs(48kHz/96kHz/192kHz

OS[1:0] = x 64fs ( default )

**Result::

(1) Fs:48kHz⇒96kHz(D..Range=111dB)

(2) Fs：192kHz⇒96kHz(D.Range=114dB)

Note; customer syas it occurs in PCM1795 EVM once a 10times.

-----------------------

Best Regards

 

  • 0
    TI__Guru**** 189401 points

    Hi, Shibatani-san,

    Wow, that is really odd! Let us look into this for you.

    -d2

    PS shouldn't you be on vacation?!?!?!

  • 0 in reply to Don Dapkus
    Mastermind 6205 points

    Don-san,

    Hello,

    thank you for your reply.

    This is additional infrmation.

    << Register setting >>

    The diefference  between customer's setting and  default  of PCM1795  is as following. Other is same as default


    FMT[2:0]       100   32bit  I2S
    DFMS            1　　 External digifil stereo 
    DZ[1:0]        01　   DSD zero Output enable
       

    (PCM mode is selected....)
    DSD        0   DSD desabled
    DFTH      0   Internal D.F enabled 

    <<Frequency table is following>>


    SCK(fs) 512 512 512 256 256 128 128
    SCK(MHz) 16.384 22.5792 24.576 22.5792 24.576 22.5792 24.576
    BCK(fs) 64 64 64 64 64 64 64
    BCK(MHz) 2.048 2.8224 3.072 5.6448 6.144 11.2896 12.288
    LRCK(fs) 1 1 1 1 1 1 1
    LRCK(kHz) 32 44.1 48 88.2 96 176.4 192

    >>Phenomenon >>

    change from 192KHz to 96KHz ; then DR= 114dB

    change from 48KHz to 96KHz, ;then DR=111dB

     

    Is there anything wrong for PCM1795 setting?

    I would want to your advise.

    Best Regards