I'm developing a device that utilizes both ADC and DAC, and I have realized that my DAC output, which is fed into the op amp, is de-facto almost floating, since op amp has high input impedance. Both DAC and ADC are on the MCU now (STM32G071KBT6), although for some time they were discreet components, which doesn't matter much, I guess.
I tried to google some stuff, and only found out that lines that end up with Hi-Z are susceptible for noise, which makes sense to me, but nothing more specific.
Also, some discreet DACs have max output capacitance in datasheet, which is usually of order of 1000pF, some a bit more, some a bit less (others never mention output capacitance).
I tried to google specifically my question, but couldn't find any reasonable answer.
Should I have some large pulldown resistor on DAC output to add it some stability and noise resistance? Some 47k (which are everywhere on my PCB, so another one won't hurt). Why, why not? (I would also really love to be able to go close to 0V output).
What about ADC? My ADC is fed from the voltage divider from the current sense amplifier, total resistance of that one is ~15k (5V->3V3, 4.7k/9.12k to produce 3.299 from 5V to stay in range, will have to account for tolerance too, probably in software).
If I fed my ADC (input) from op amp directly, it would create same problem as with DAC output into op amp. Would I need a pd resistor there? What about capacitor on the ADC line?
Summary of questions:
ADC input: capacitors and pd resistors? Yes/No, when, why?
DAC output: capacitors and pd resistors? Yes/No, when, why?