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PCM3793A Input Signal when powered off

takishin
Expert 2360 points
Other Parts Discussed in Thread: PCM3793A

Our customer has a question about PCM3793A. 

I'm posting the question for the customer:

++++++++++++++++++++++++++++++++++++++++++++++

Can signals input to the analog input pins of the PCM3793A chip when the chip is powered off?

We need partial power-down with PCM3793A powered off.
But the analog input pins of the chip are connected with output pins of a microphone amplifier
which is always powered on. (the analog signal is about 0.5Vrms)

++++++++++++++++++++++++++++++++++++++++++++++

Thanks in advance.

Best regards,
Takishin

  • 0
    Expert 2360 points
    Hi there,

    I guess the inputs of the chip does not have diodes(input protection circuitry),
    because "Input Voltage" is within -0.3V to 4V in ABSOLUTE MAXIMUM RATINGS of datasheet.
    That doesn't influence VDD rail.

    So, I think they can input the signals to the analog input pins of the PCM3793A
    when the chip is powered off.

    Is this correct?

    Best regards,
    Takishin
  • 0 in reply to takishin
    TI__Mastermind 27880 points
    Hi Takishin,

    There are ESD didoes on the pins, this means that when a voltage is applied current will flow as they pass through the ESD diode. This will offset some current savings by turning off the supply to the part. There is also a possibility that the ESD diode will be damaged if current of the input is not limited by a series resistance. With this understanding, if you stay below the absolute maximum voltage rating for the pin and limit the current the part should be fine.

    Justin
  • 0 in reply to Justin Bohr
    Expert 2360 points
    Hello Justin,

    Thank you for your reply.
    I understand.

    I will report this information to our customer.

    Best regards,
    Takishin