I would suggest a low drop out regulator from your PIC 5 Volts supply.

You can look at on semiconductors or linear technology websites. On
semiconductors has a selection tool that is very useful.

Selon Debbie <cyberia429-piclist@yahoo.com.au>:

> PICers ... I have a bit of a dilemma selecting an IR sensor.  They're NaPion
> motion sensors that are made by Matsushita. They come in both digital and
> analgue o/p: it's digital that I need. I've used them before and they're
> pretty
> damn good.
>
> The one's I'm talking about are here -->
> http://pewa.panasonic.com/pcsd/product/sens/select_motion.html
>
> The dilemma -->
> They come in a standard version that works on 5V but its quiescent drain is
> 170uA to 300uA
>
> However, they now offer an ultra-low standby current version that's rated at
> 46
> to 60 uA quiescent.
>
> That's MUCH better for a battery operated device. BUT, the ultra-low Iq
> version
> only works on 3V.
>
> Okaaaay, I have a 12V, 7.5Ah system and the PIC's (16F84) voltage is
> regulated
> down to 5V using a 78LS05. Not sure what its standby drain is but must be
> pretty low as the battery lasts for weeks.
>
> The QUESTION: what ultra-low Iq 3V regulators come to mind?
>
> If I go with the 3V sensor, I'd have to drop 2V off the 5V rail or 9V off the
> 12V rail. This when I'm pulling, hopefully, total standby current of <150uA
> (inc. both regulators, the PIC in sleep mode and the IR sensor)
>
> What would people say is the best way to go?
>
> These sensors aren't all that cheap and I need about 6, so I probly want to
> get
> it right first time. :(
>
> Thanks in advance for advice.
>
> Best - Debbie :)
>
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