Rant about useless internal voltage references.

I originally titled this :Useless internal voltage references" but decided
to change it.

I'm interested in using a processor with (at least) 10 bit analog to digital
converter accuracy.
Most with internal A/D have band gap references. These have broad nominal
voltage specs compared with the accuracy of the converter. eg 1.11 / 1.23 /
1.34 min/typical/max  or about +_/- 10%. OK - maybe we can calibrate this
initially. How good is it over temperature and voltage. Let's check the data
sheet. Nope. No information whatsoever. It's hardly worth providing a +/-
10% reference with absolutely no information on its characteristics. One may
well be better off dividing down and smoothing Vdd !

Looks like an external reference is liable to be essential. OK, I knew that
anyway, but you'd think you'd get some help from the makers.

What are other people doing?
Are there a whole world of people out there using 10 bit A/Ds with a 10%
uncharacterised reference ? ;-)




        Russell McMahon

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