What is the equivalent input circuit for the ADCs on the STM32F334?

[PRuss.1]

Hi,

I've been looking around in the documentation, and I can't find anywhere what the equivalent input circuit for the ADCs on the STM32F334 are. What is the input capacitance? What is the equivalent series resistance of the analog mux? What is the sample cap size? Is there internal buffering? If so, is it before or after the mux? What's the equivalent input noise?

Thanks,

Peter

[S.Ma]

Usually careful reading the electrical tables in the datasheet provide such information to all readers.

On most MCU, ADC are SAR (successive approximation ADC with binary search scheme, 12 bit being nearly the best state of the art perf vs size & cost).

The ADC input Die Pad itself would be few pF (always present), then there would be an analog switch of few kOhm (maybe 2 kOhm?) which is turned on during the sampling time programmed on the ADC, charging a sampling (hold) capacitor of few pF (maybe 5-6?). Usually assume the capacitor is not starting from 0V when sampling time starts, it needs time to settle to the external signal voltage.

The analog signal going to the ADC should be low impedence. Using a simple resistor divider won't work and regular voltage dips on the oscilloscope will appear. Using a low offset op-amp as follower, or a big decoupling cap for slow signals will help.

[AScha.3]

most users first look in ds and rm :

 

+ if you see a buffer here, you know... Is there internal buffering?