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Impedance of ADC pins powered up/down

Question asked by FridgeFreezer on Aug 24, 2010
Latest reply on Sep 11, 2010 by TomE

We are using an MCF52259 and want to wire the RTC battery to an ADC pin to read its state of charge, but obviously with battery life being finite we don't want to draw too much current from it.

 

Does anyone know, or is it in a data sheet somewhere, what the impedance of the ADC pins is both when the micro is powered up and when it's powered down? I have looked in the micro reference manual but there's no data on this.

 

We are going to measure it with a DMM as well, but obviously it's nice to have some official numbers to go on.

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