I also will add that I have 5 data loggers built. One works fine with a 1.25V reference but the others do not. So it appears that there is a fairly wide process variation on this parameter. Thus don't assume that you are OK just because one part works! Conveniently enough I can't find an LT1790 2.048V reference anywhere but digikey and they have a backorder. Estimated ship date 2/4/2004. Hmmm... I only really need one unit finished for the initial installation (the probes will be buried in an enormous compost pile as it is turned over the course of a month or so) so I am considering just going with the one that works at 1.25V first but I really need to get these chips asap. Anyone else know where I could pick up 10 of em? Nick ----- Original Message ----- From: "Spehro Pefhany" To: Sent: Sunday, February 08, 2004 9:26 PM Subject: Re: [PICLIST] [PIC]: Minimum A/D VREF Voltage For F818 ? > At 08:04 PM 2/8/2004 -0700, you wrote: > >I thought I noticed a discussion about minimum +VREF values when USING > >the Mid-Range PIC A/D converter. I using 16F818, but I couldn't locate > >any documentation about such a limit anywhere. > > > >Does anybody know if there is a minimum +VREF voltage and if so, what is it? > > It's defined by parameters A21, A22 and A25. > > The difference between Vref+ and Vref- must be at least 2.0V (A22) > > AND both Vref+ and Vref- must be between AVdd and AVss (or less than 300mV > outside). (A21, A25) > > Best regards, > > Spehro Pefhany --"it's the network..." "The Journey is the reward" > speff@interlog.com Info for manufacturers: http://www.trexon.com > Embedded software/hardware/analog Info for designers: http://www.speff.com > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.