James Nick Sears wrote:
> 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.

The "power of 2" voltage references are pretty silly in my opinion when
you've got even a minimum of computational power available (like a PIC).  I
would stick with the lower price and better availability of more native band
gap references.  It shouldn't matter much what the value is, as long as it's
within the useable range and well specified.  I use the LM385 often in
situations like this.

Note also that the reference need not be driving a Vref pin.  You can set
the A/D range from Vss to Vdd and make the reference another A/D input.  I'm
doing something like that on a project now where I want to measure the
battery voltage that is also running the PIC.


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