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ADS8689: How to power?

MarcoD
Prodigy 30 points
Part Number: ADS8689

Hello,

I just bought this part for a school project. I am wondering what the best way to power this ADC is. Do I need two separate power supplies for AVDD and DVDD? I am going to be communicating with it using a Raspberry Pi so I should be able to use 3.3v from that for DVDD, I'm just not sure about AVDD.

Thanks,

Marco 

  • 0
    TI__Mastermind 39645 points
    Hi Marco,
    The AVDD supply range specified in ADS8689 datasheet is 4.75V to 5.25V, a +5V power supply is recommended for AVDD, so you can use 3.3V for DVDD but you have to provide a +5V supply for AVDD. Also, the supplies should be decoupled with AGND/DGND with a proper capacitor on each supply pin. Please refer to the power supply recommendations and layout guidelines in the datasheet.
    Best regards
    Dale
  • 0 in reply to Dale Li
    Prodigy 30 points

    Thanks for the reply Dale,
    I think I was able to figure that out after reading the datasheet some more.
    I'm still confused on if the +5V and 3.3V can be pulled from the same source (i.e using the 5V and 3.3V pins on the Pi) or must they be two complete different sources?

  • 0 in reply to MarcoD
    TI__Mastermind 39645 points

    Hi Marco,

    The source for the supplies on the ADC is not limited, but a clean power supply is always recommended especially for AVDD, otherwise, it will degrade the performance specified in ADC's datasheet because the power-supply rejection ability(PSRR) on the ADC is variable and limited with ripple/noise frequency, please refer to the below graph from ADS8689's datasheet, this is the reason why we often use LDO to provide a clean analog power supply to ADC on our EVM boards or reference designs, for example, TPS7A4700 or TPS7A4901. I hope this explanation is helpful for you, thanks.

    Best regards

    Dale