And the computation below was done using 'typical' numbers. We all now we should never design to the 'typical', right? Bob Ammerman RAm Systems ----- Original Message ----- From: "Michael Rigby-Jones" To: Sent: Wednesday, June 12, 2002 3:10 AM Subject: Re: [PIC]:strange analog in problem > > -----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 > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics