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ADC Source Impedance

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I've searched the XBee Manual (XBee®/XBee-PRO® ZB RF Modules) for S2 hardware for the ADC tolerated source impedance and couldn't find it.

Where can I find that information?


Carlos Vicente
asked May 1, 2014 in RF Solutions and XBee by cvicente New to the Community (6 points)

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2 Answers

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They can only source about 2mA for each pin and no more than 40 mA total
answered May 1, 2014 by mvut Veteran of the Digi Community (12,779 points)
I'm kinda green on electronics, so I don't actually follow...
I mean, if I have a current of 2mA on a ADC pin with a maximum voltage of 1.2V, does that mean that the maximum source impedance for that ADC pin is 600ohms?
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Yes that would mean that you are at the max source impedance of 600 Ohms.
answered May 2, 2014 by mvut Veteran of the Digi Community (12,779 points)
But wouldn't that mean that, for instance, if I would have to use a voltage divider as input of an ADC pin (to cut-off some sensor output for example), the resistances to use would have to be a bit low?

For instance, for my purpose I was thinking about using for a voltage divider resistances of 12k and 27k. Thus, I would get from the point of view of the ADC pin a impedance around 8.3K which is well above the 600 ohms. So, in this case... should I lower the resistances values?