ADC input impedance

[kostyan5]

Does anyone know... what is the input impedance of the ADC? Also, what are the resistor values of the attenuator pad?

[ayavilevich]

I am also interested to know this. Wasn't able to find this in the datasheet.

[hgptamn]

I would also like to know that; couldn't find it either!

[BuddyCasino]

Suddenly I want to know these things as well, even though I have absolutely no use for this information. I just love drama.

[PiMaker]

Though I don't have any hard values for input impedance since they aren't listed in the spec, it would seem dependent on which ADC you select. SAR ADC1 has a built-in LNA, so you should be able to configure it as a unity gain amplifier which as I'm sure you know will give you extremely low input impedance. The other ADCs don't have this feature so I presume the input impedance will be high like most microcontrollers. If you don't want jitter or slow sample issues, then you need to either use the integrated LNA or use an external op amp to feed the ADC.

[longjf]

I just used a voltage divider on the first input two 10K resistors... I observed 2.49 volts on the pin with two 10K resistors splitting the reference in half or so. I get 37K as a nominal impedance....

[Tnarain5]

Hey, i was using MAX4466 for ADC input but i have a lots of noise in input. i tried adding 0.03uF capacitor but noise still exists.