ADC input impedance

kostyan5
Posts: 49
Joined: Mon Mar 06, 2017 3:16 pm

ADC input impedance

Postby kostyan5 » Sun Oct 01, 2017 6:34 pm

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

ayavilevich
Posts: 5
Joined: Sat Oct 07, 2017 8:50 am

Re: ADC input impedance

Postby ayavilevich » Mon Oct 23, 2017 4:56 pm

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

hgptamn
Posts: 26
Joined: Mon Oct 16, 2017 4:47 pm

Re: ADC input impedance

Postby hgptamn » Tue Jan 30, 2018 1:48 pm

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

BuddyCasino
Posts: 255
Joined: Sun Jun 19, 2016 12:00 am

Re: ADC input impedance

Postby BuddyCasino » Tue Jan 30, 2018 4:02 pm

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

PiMaker
Posts: 3
Joined: Mon Feb 12, 2018 5:37 pm

Re: ADC input impedance

Postby PiMaker » Tue Feb 13, 2018 3:39 pm

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.

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