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PCM1754: driver issue

user5883945
Expert 1886 points
Part Number: PCM1754
Other Parts Discussed in Thread: PCM1794

Tool/software:

Dears,

   

SCH

 

Configure as FMT=0

Customer's processor is ADSP-21565, with a main clock frequency of 12.288MHz (connected to the main clock input of PCM1794), and is also connected to ADSP-21565，21565 to generate I2S bit clock (1.024MHz) and synchronous clock (16kHz) through frequency division, as shown in the following figure

 

The data output of I2S remains at a low level, as shown in the following figure

There is a problem where the I2S data output is low and there is a large amount of noise in the simulated output (as shown in the figure below). Could you please help me figure out what is going on? Thank you

  • 0
    TI__Mastermind 30791 points

    Hello,

    I don't see any issue with the schematic and it matches with the recommended schematic in data sheet,  Also the BCK and SCK values are okay for 2 channel, 32bit, 16k sampling frequency with SCK being 768xfs

    Few things to check,:

    1-you need to plot all the I2S signals on the same screen and make sure it is matching with figure 23 of datasheet. ( My be data in is not I2S, may be it is RJ or something that is not supposed to be, please verify it) .

    2-What is the reading on VCOM? when DAC is not operating, the outputs should be sitting at VCOM (0.5VCC). It looks like the vouts are sitting at a wrong voltage. Remove the cap after the ouput and connect directly to active LP filter and just use the decoupling that you have at its output. In fact i would monitor the outputs right after the DAC, not at the output of the amplifiersto make sure issue is within the DAC.

    Regards,

    Arash

  • 0 in reply to Arash Loloee
    Prodigy 10 points

    1,this is our i2s signal

    2, VCOM

  • 0 in reply to dd ff
    TI__Mastermind 30791 points

    Hello,

    The first plot shows the input is not toggling, if this was done intentionally  to check the outputs are  pulling to VCC/2, I need those waveforms to be verified. 

    From the plot your VCOM is not sitting at VCC/2. 

    I would still need to see the I2S signals (BCLK,FSYNC and DIN)  captured in the same window to verify the format of the data in. This is a 24bit part,  Can you send a 24bit data ( and make sure the input is  toggling,  not sitting at low) and verify the supply is correctly reaching the device at its pins. Also verify the capacitor connected to VCOM is ok (value and  polarity if applicable) 

    Regards,

    Arash