Friday 20 May 2016

Required output impedance for ADC input?


On the Atmel AVR 328P on the Arduino Uno, the ADC's an R(ain) value is 100Mohm - which I assume is the ADC input impedance? However, in the datasheet it says "The ADC is optimized for analog signals with an output impedance of approximately 10 kohm or less."


How do you figure out the ideal output impedance to work with the ADC? I'm trying to figure out how this applies to other discrete ADCs which have an input impedance that varies with sampling frequency... for example on one part the input impedance varies from 125kohm to 65Mohm. How would I figure out what the max allowable input impedance should be?


Also - am I even asking the right questions here or am I missing something huge?




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