[sdiy] Temperature Compensated Exponential Converter Using SSM2164

[Dave Leith]

Just thought I'd mention that the specs for the ADR01  (mentioned a
few emails back) say

ADR01/ADR02/ADR03 pin compatible to industry-
standard REF01/REF02/REF03

not sue if it's any better but it  does have a few very interesting
features and good specs.

Digikey also carries this


On 9/6/09, David G. Dixon <dixon at interchange.ubc.ca> wrote:
> > > 1.  The "obvious" option:  Take 15V straight from the supply rail
>  > > and divide
>  > > it down according to the scheme as outlined before.  I'm presuming
>  > > that the
>  > > supply rail won't bounce all over the place!
>  >
>  > WRONG - supply rails bounce all over the place.  Why do you think op-
>  > amp manufacturers specify PSRR?  UNLESS you have a circuit which is
>  > ratiometric so doesn't care about the exact value (and even then I
>  > still think its dumb - why let supply rail noise into your circuit?)
>  > never rely on the supply rails being 'constant' - they are anything
>  > but constant.
>
>
> Point taken.
>
>
>  > > 2.  The "clever" option:  Drop the rail voltage with a zener diode
>  > > rated between 4.7 and 5.6 volts...
>  >
>  > Ok, not so dumb as using the supply rails, and fine if you're not
>  > concerned about temperature stability too much. 0.01%/K = 100ppm/K.
>  > Not bad.
>
>
> ...and about all one could expect from the metal-film resistors in the
>  circuit, in any case.
>
>
>  > Better yet try something designed for this, like a bandgap or buried
>  > zener.  For example, the REF02C gives you +5V at 20ppm/C typical,
>  > max. 65ppm/C.  Bandgap ref. diodes give you similar stability, e.g.
>  > the ZRB500 will give you typ. 15ppm/C.
>
>
> Neil, this is the first I've ever heard of these parts!
>
>  I see that Digikey carries REF02 5V references from Texas Instruments for
>  $3.11 for 15ppm/K, and $5.04 for 10ppm/K.  This seems a fairly small price
>  to pay for rock-solid tempco.
>
>  Thanks for the tip!
>
>
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