I was wondering if you could tell me the effective output impedance of Vcm0 (the Common-Mode Voltage for DAC0 External TIA)? The data sheet states that the output impedance of the reference output is quite low (50 mOhms) but I did not find any mention of the output impedance of Vcm0.
I am asking because I am using the AD3551R with a fully differential (input/output) amplifier ADA4945, and I initially included a feedback RC on the +FB (to the Vcm0, connected to IN-); I think this was a mistake, but I thought that it should not matter if Vcm0 had a low output impedance. I tried to simulate the setup, but I needed to include about a 10 kOhm ouput impedance for Vcm0 to match measurements. (specifically, with a 3.2 kOhm / 220 pF feedback, I was seeing a 2.4 V differential dc offset).
(I am now doing something very similar to figure 3 of https://www.analog.com/en/resources/technical-articles/using-a-differential-io-amplifier-in-single-ended-applications.html , which seems to work as expected.)
Thank you for your help,
Nathan
