> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of Jan-Erik Soderholm
> Sent: 29 July 2010 15:15
> To: Microcontroller discussion list - Public.
> Subject: Current drawn by an ANx input ? 16F690
>=20
> Scenario:
> PICkit2 with low-pin-count board (16F690).
>=20
> That board has a 10k pot with a 1 k resistor
> connected between the wiper and the AN0 input.
>=20
> Now, when running the ADC-demo program (number 4 of the
> lessons, called ADC.ASM), I can see a larger then I
> expected voltage drop across the 1 k resistor. Up to
> 0.85 V when the pot is at the 5V end. That is, there
> must go aprox 0.85 mA into the RA0/AN0 pin.
>=20
> Is that expected ? I've read the datasheet back and forth
> but can not find any note sayig that the AN0 input should
> draw that amount of current. A few uA's leakage maybe...

Yes that is unexpected in normal operation, the average current into an
analog pin is very small, certainly in the uA's.

Is the top of your potentiometer definitely powered from the PIC's Vdd
rail?  If you exceed Vdd then you will be pumping current into the PICs
protection diodes.

Regards

Mike

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