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ADS8584S: AVDD power details clarifications

Fimmy Joy
Prodigy 50 points
Part Number: ADS8584S
Other Parts Discussed in Thread: ADS8588SEVM-PDK, TPS7A47

We are using ADC with MPN : ADS8584S . As understood from datasheet we require a clean power supply for AVDD pins .

1.We had referred to  ADS8588SEVM-PDK User's Guide . In this board supply is from PHI controller board . Can i get the reference schematics for PHI controller board?

2.We are getting  5v to the ADC card directly from  bought out power supply module . Kindly suggest how to make the 5v from power supply module as clean 5v to use for AVDD pins. In the reference evaluation schematics of ADS8588SEVM-PDK User's Guide 5.5 v from PHI controller board is converted to 5v using TPS7A47. Kindly suggest what has to be done in this case where i am getting 5V to the board externally with 1-2% ripple.

3.If we are using only 2 channels of ADC is there anything that we have to take care .

Thanks & Regards,
Fimmy Joy

  • +1
    TI__Mastermind 39295 points

    Hi Fimmy,

    Please see the answers below:

    1. Unfortunately, the schematic of PHI controller card can not be shared. The 5.5V power supply is generated from a charge pump and the 3.3V is generated from a PMIC device on the PHI controller card.

    2.A LDO is strongly suggested to generate a clean power supply for the ADC especially for 5V AVDD. Otherwise, you may not be able to achieve the performance specified in the ADC data sheet. The external 5V can be connected to the J11 and selected by the J10 for the ADC, the 3.3V can be connected to the J12 on the EVM.

    Another possible solution is using the TPS7A4700 LDO on the ADS8588SEVM which can generate a clean 5V supply for the ADC when an external power supply is used. However, you have to use >5.5V external power supply and the power supply can be connected to the input of the U4 LDO through a blue wire.

    3. ADS8584S is 4-ch simultaneous-sampling ADC and each channel has a dedicated signal-chain including ADC, so nothing is special when only 2 channels are used. You can convert 2 channels by using only CONVSTA or CONVSTB, or you can ignore 2-channel data when you get the data for all channels.

    Best regards,

    Dale