ADC pins input resistance

I’m trying to measure both the battery voltage and an external voltage on HTCC-AB02S’ ADC1 and calculate the error based on the resistor network around thet pin. I can find the resistance values of the external components but for the final result I’d also need the internal ADC pin resistance of the ASR6502.

Does anyone have any info on that?

facing same issue here, did you get any conclusions?

I didn’t loose much time with this, I plotted the known voltage vs. measured voltage and calculated the non-linear correction factors. (I used an online tool to fit the function - I don’t exactly remember which one).
It worked kind of good enough but in the long run I decided to use external I2C current/voltage monitors (INA219) for better precision anyway so I didn’t go much further with this.

Hope this helps,