At 12:57 PM 10/31/2004 -0700, you wrote:
>Hello,
>I am working on a project which is powered from +/-5V and uses some
>AD5235 digital potentiometers which require +/- 2.25 to 2.75 V for
>supply. My question is, what is the best way to generate the +/- 2.5V
>supply from my +/-5V supply. Each supply only needs to handle two
>AD5235's, so that's a maxium current of about 70mA worst case. Right
>now I have chosen a LM317L and LM337L with a couple of resistors and
>capacitors to make a linear regulator. Are there any better linear
>regulators out there? It seem's there are slim pickings for negative
>regulators that can do -2.5V. My requirements are: small footprint,
>multiple sources or confidence that I will be able to get a workable
>part for the next 20-30 years (not too critical, since the AD5235
>probably does not fall into this category, but it would be nice). Cost
>is less of an issue, but of course the cheaper the better. I think a
>switcher is certianly overkill for this application since most of the
>time the AD5235s will be consuming less than 2mA.
>Thanks,
>Glenn

Those parts sound like a quite reasonable choice given the constraints.

There are not many adjustable negative regulators- LM2991 is another, but I
don't see any advantage in this case. If you're doing the project for
a competitor, consider the MAX1735 (low power, low parts count, fixed -2.5V).

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




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