ADA4528-1 as an ADC Reference Buffer

Can the ADA4528-1 handle large capacitive loads ( > 4.7µF) and drive the reference of a high precision sigma-delta like the AD7173-8?

I do not want to add source resistance between the output of the amp and the input of the reference of the ADC.  Will the 200kHz noise from the chopping frequency affect the performance of the converter without a filter?  Perhaps a snubber network is advised if the ADA4528 is to be used in this application?

- James

  • This discussion has been ongoing last week via email and closed.

    In summary, below is an excerpt of the email exchange:

    " I have sometimes seen customer use ZD amps to buffer a reference output. What they would do is LPF the output of the amp. This however increases the impedance seen at the ADC REF pin (I believe the offset voltage due to current flowing through the resistance can be calibrated out). Also, the ADA4528 cannot drive 4.7uF without any compensation. It can only safely drive up to maybe 200-300pF. So, in this case, having an post RC network serves to isolate the cap load, stabilize the amp and provide filtering.

    We haven’t tested any reference buffers with the AD717x family of ADCs for two reasons:

    1. The references we’ve used and recommended are able to drive the ADC without additional buffering required, just external RC. These are the ADR44x and ADR455x family of references.
    2. The ADC has integrated reference buffers eliminating the need for external buffers. These buffers are not very low noise but still should be lower noise than the reference itself. The integrated buffers are chopped also so no need to worry about 1/f noise or drift. "