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PCM5122 default setting in I2C mode

Andreas von Ow
Prodigy 80 points
Other Parts Discussed in Thread: PCM5122

Hello,

I have successfully used a PCM5122 in HW mode and have now a new design where the DAC is set to run in I2C mode.

My understanding from the datasheet is, that reset puts all registers in default mode where the device outputs an analog signal without signal processing. I'm using VREF mode, VCOM pin is tied to ground. In HW mode, the PLL uses a clock auto set mode. According to the datasheet, this is the default setting after reset, so I assume this is the same in I2C mode (default value for DCAS bit (Page 0/Register 37) = 0) ... on the other hand, according to section 8.3.6.3 "Clock Slave Mode With BCK PLL to Generate Internal Clocks (3-Wire PCM)" of the datasheet the PLL registers need to be initialized in SW mode.

Question 1: Is it correct, that after reset, the signal processing is straight output = input (no filters, now dynamics processing)?

Question 2: Is the device in clock auto set mode after reset?

Question 3: Is the internal charge pump only working if PLL settings are correct (= VNEG pin is only -3.3V if PLL settings are ok)? 

Question 4: Is it possible to run the PCM5122 in its default mode without sending any I2C initialization commands? 

Thank you for clarification of these points

Andy

  • 0
    TI__Mastermind 27900 points
    Hi Andreas,

    Q1. Yes the part should default to the FIR filter in salve made and be able to pass audio.

    Q2. The device should be in slave mode but is not in a mode to run without a master clock. For this you will need to disable the SCK halt bit in register 0x25.

    Q3. The clocks must be correct for the charge pump to be functioning. If there is any clock errors, the charge pump will be turned off and the device should be in a sleep mode.

    Q4. It is possible to run the PCM5122 from default if you are using 4 wire I2S and in slave mode.

    Justin
  • 0 in reply to Justin Bohr
    Prodigy 80 points

    Hi Justin,

    thank you for the quick and clear answers. It seems my design needs some SW support to work properly. 

    Best regards

    Andy