Buffering ADC Reference

I see in most of your application circuits you use an AD8031 to buffer the ADC reference voltage (Vref), why is that?

  • Its a good idea to buffer the reference votlage (Vref) coming out of an ADC when used to drive the Vocm pin of a differential driver. This does a few things for your circuit.

    1. The Vref pin of the ADC cannot drive heavy loads, so the op amp unity gain buffer isolates the Vref pin and prevents loading it down.
    2. The output of AD8031 has a low output impedance and it acts as an excellent voltage source (i.e. low impedance and steady votlage supply) 
    3. The AD8031 also drives capacitive loads very well and in most cases there is a substaintial cap at the output of the amplifier to provide stored charge. It also provides a low impedance path to ground through the cap to prevent unwanted noise from entering the Vocm pin.

    So as you can see, adding a Vref buffer is a good idea and helps improve system performance.

    Regards

    John

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