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Power up requirements of ADS7953 for analog and digital supplies

Michelle Smekal
Prodigy 130 points
Other Parts Discussed in Thread: ADS7953

I am using the ADS7953 part. During power-up of ADS7953 and our 2 USB devices, is it OK to power-on digital 2.5 and 1.8 supplies, before power-on of analog 4.4 volt supply?

I see on the datasheet it says "analog supply is always greater than or equal to the digital supply", I'm not sure if this includes during power up.

  • 0
    TI__Mastermind 45785 points
    Hi Michelle,
    The specification in ADS7953 datasheet(Page 8) states that Digital I/O-supply voltage(+VBD) can range between +1.7V and Analog power-supply(+VA), so as a best practice, +VA should be powered up before or at the same time as +VBD. The Absolute Maximum Ratings section also shows that the signal input(AINP or CHn) has a restriction in that these inputs cannot exceed +VA + 0.3 V , this states that if an analog signal is present before analog power-supply, the analog core powers up in a highly probable latched-up state. This is typically a nondestructive condition, but the current through +VA can be cousumed higher than the normal current and cause the ADC to become quite hot at that time.
    I hope this is useful for you. Thanks for your post.

    Best regards
    Dale Li
  • 0 in reply to Dale Li
    Prodigy 130 points
    I'm still not clear on the ramifications from the first section of your post if my digital supplies (2p5 and 1p8) can be powered on slightly before my analog of 4p4V supply.
  • 0 in reply to Michelle Smekal
    TI__Mastermind 45785 points

    Hi Michelle,

    +VA should be powered up before or at the same time as +VBD, and only one digital power-supply on this ADC(+VBD).

    Best regards

    Dale Li