Re: Help with power issues

On Mar 31, 9:44 pm, "m...@xxxxxxxxx" <m...@xxxxxxxxx> wrote:
On Mar 31, 1:21 pm, Eeyore <rabbitsfriendsandrelati...@xxxxxxxxxxx>
wrote:



James Arthur wrote:
linnix wrote:
On Mar 31, 10:58 am, linnix <m...@xxxxxxxxxxxxxxxxxx> wrote:
On Mar 31, 10:33 am, Eeyore <rabbitsfriendsandrelati...@xxxxxxxxxxx>
wrote:

< snip>

Suggest using micropower voltage regulators. Zeners are horrible.

Yes, but standby power is less than 100µA, with everything else off
except the µC. Active power is only for several minutes once in
several days or weeks. Standby power needs to be several months on
two CR2032.

Here is the simplified schematic:

http://linnix.com/SigmaDeltaEpilson.gif

Actually, we have considered a custom made 4V LDO with 3.5µA standby
current. But we are trying to avoid the $3000 minimum order for the
moment, until necessary, we will just stuff it with zeners or even 6
regular diodes.

Seiko Instruments has a number of uA-quiescent regulators.

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=728-...

data***:http://data***.sii-ic.com/en/voltage_regulator/S812C_E.pdf

About $0.30 @ qty 3,000, as you said.

That looks just the job.

Graham

The LDOs I've designed, as well as most of the industry these days,
has reverse polarity protection. This DIY design doesn't, and his
budget (voltage or dollars) can't tolerate a series diode.

Of course, I speak from a vacuum since I never had to design anything
for sale other than chips, so perhaps crappy engineering is the way of
the world.

If you never have to deal with the budget, then you never have to deal
with difficult issues. I know LDO is the solution from the beginning,
but they are not cheap. We gave them a single chip perfect solution
(Atmega169) with nothing else. Of course, they are coming back with
sticker shock when they put it in production.
.

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