For the AD9269:
Can the VCM pin (pin 57) be used to drive one of the ADC inputs? The datasheet does not mention either the VCM pin's output impedance or the input impedance of the ADC.
The AD8251 datasheet shows the REF input resistance to be 20kOhms, so the AD9269 VCM pin will have no problem driving this as well as one of the ADC inputs.
Remember to bypass-to-ground the ADC VCM pin, having the capacitor as close to the package pin as is reasonable.
Yes, the VCM pin has the capability to drive one of the AD9269 analog inputs. Are you planning on using VCM to drive one of the differential inputs, and apply a single ended signal to the other?
Thanks, Doug. Yes, that is exactly how I'm planning to use it. I'm also using it as a CM offset reference for a instrumentation amplifier (AD8251), which is the source of the single-ended input to the ADC. Is this arrangement acceptable, or would you recommend buffering the VCM output first?
I forgot to mention that the VCM bypass capacitor should be 0.1uF.
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