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ADS8586S: DVDD remain active and AVDD is turned on, is there any problem?

Shinichi Inoue
Guru 21646 points
Part Number: ADS8586S
Other Parts Discussed in Thread: ADS8584S

Tool/software:

Dear Specialists,

My customer is considering ADS8584S and has a question.

I would be grateful if you could advise.

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The board under development has a battery backup function.

During backup, the digital power supply (3.3V) will remain active, but the analog power supply will be turned off.

If the ADC only receives digital power (SPI, etc. will also be active) and analog power is not supplied, will there be any problems with the device?

There is a possibility that an analog signal will be input.

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Expert 8756 points

    Hi Shinichi-san,

    Thanks for your question. This should be okay, as the digital input is only dependent on the DVDD rail. Please note, no input signals may be applied while AVDD is powered down though. If an analog input signal is applied while AVDD is powered down, this may cause damage to the device.

    However, I would recommend issuing a reset after the supplies are both powered up to ensure proper operation, per the power supply section in the datasheet:

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Guru 21646 points

    Hi Samiha,

    Thank you for your reply.

    I'd like to confirm.

    According to the absolute maximum rating, analog input voltage to AGND is -15V to +15V.

    I think this means analog input is acceptable when AVDD is turned off.

    Are there any other reasons why this is unacceptable?

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

  • +1 in reply to Shinichi Inoue
    TI__Expert 8756 points

    Hi Shinichi-san,

    I confirmed with the team and you are correct! You may apply up to +/-15V to the analog inputs while AVDD is powered down.

    Best regards,

    Samiha

  • 0 in reply to Samiha Sharif
    Guru 21646 points

    Hi Samiha,

    Thank you for your reply.

    Samiha Sharif said:
    You may apply up to +/-15V to the analog inputs while AVDD is powered down.

    I understand. 

    I'll share this information with the customer.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi