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PCM1864: Power Sequencing Question

David C
Expert 3350 points
Part Number: PCM1864


There could be a case where AVDD is up before DVDD/IOVDD.  Section 11.4 only talks about powering the 3 rails without an order or rating for differences.

Is this going to be a problem?

  • 0
    TI__Mastermind 23050 points

    Hi David,

    I apologize for the delayed response, we did not have any information readily available on this so I took some measurements in the lab using an EVM and can at least describe the behavior. With AVDD applied without DVDD or IOVDD the current draw on AVDD starts out at ~38mA and slowly drops to 24mA. In normal operation, the AVDD current is ~31mA, so there is some increased leakage and uncertainty in the state of the device, it's difficult to say what exactly is happening in this mode, but once DVDD/IOVDD is applied, the current jumps to 31mA and the device enters the "run" state so it appears to recover once these rails are powered. Note, if AVDD and DVDD/IOVDD have been powered up and DVDD/IOVDD is lost, the current on AVDD will drop to 1.2mA, indicating the devices goes into an analog power down state. In the reverse case where DVDD/IOVDD is applied first, the device will recognize AVDD is missing and hold the chip in power down until AVDD is applied. I hope this helps!

    Best,

    Zak