> -----Original Message-----
> From: Dwayne Reid [SMTP:dwayner@PLANET.EON.NET]
> Sent: Wednesday, June 12, 2002 1:53 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]:strange analog in problem
>
> True.  I did not mean to imply that the cap cures all the effects of too
> high a source impedance and perhaps I should have stated that in my
> initial
> post.  But the predominant error source seems to be from the S/H cap and
> not leakage.
>
The datasheet shows a typical leakage current of 500nA.  With a 100K source
impedance this could give an error of 100k*500n = 50mV.  On a typical PIC
using (5v) Vcc as a reference this would give around 10 counts of error
(around 3.3 bits).  If this was constant then it may not be a problem, but
leakage current by their very nature are quite temperature dependant.

Regards

Mike

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