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AIC3254 wrong sampling rate

julien1986
Intellectual 385 points

Hi,


Since few year ago, we are using the AIC3254 on different board.

A few a month ago we have made a new board .The hardware almost the same that the old board.

The configuration that we use has been used also since few year and it's very stable.

The codec works on master mode with 8Khz sampling rate with input frequency of 12MHz. We are using HPL ouput in common mode and microphone input in diffential mode.

We have found this problem:

If we put a low impedance (less than 100 Ohms)on the HPL output. The WCLK  decreases  at 7800Hz.

We think that is hardware issue... Have you got any idea?

Best regards,

  • 0
    TI__Guru**** 189401 points

    Hi, Julian,

    That is very strange. I would check the power supply voltages at the pins to make sure they are not dropping too much due to the load current. 100 ohms should be no problem for this device, so I suspect a PCB layout issue.

    -d2

  • 0 in reply to Don Dapkus
    Intellectual 385 points

    Hi,

    Thank you for your answer.

    Check the power supply is the first that I have done. I didn't see noise or voltage drop...

    I think there is an PLL instability. Maybe some bad or wrong component has been put on the board.

    Have you got any  idea about which component or signal could produce a PLL instability ?