Gregg Wrote,


> I saw your post today about your success with using the PNP
> transistor-based brownout circuit from Microchip.  I haven't used a
> brownout cicuit in my new design, and though I haven't seen any
> problems, I need to play it safe.
>
> I'm running an LF84, from 3 AAA cells.  The cells are expected to
> run down to about 3 volts during use, but there;s nothing to prevent
> a careless user from running them to zero... hence my concern for a
> brownout cicuit.
>
> I was hoping you could share some of your experiences in this area
> ... my main concern with the PNP circuit is the constant battery
> drain from transistor's bleeder path.  Since I'm completely battery
> powered, that could be a real killer.  Did you find a clever way to
> reduce the drain?


Unfortunately my application was in a 120 volt appliance where I can
waste megawatts if I want to.  <slight exaggeration>  I also need to
be very low cost.  I doubt the PNP transistor trick is the right
thing for your application, unless you're building toys.


Also, what is the danger in a brownout?  In my application, a stuck
program could mean a heating element turns on, resulting in a melted
appliance and a mad customer.  In a toy, who cares?  In a cell phone,
you might care.  I doubt a battery powered application has enough
power available to go into a self-destuctive mode, maybe it just
wouldn't work right, and the customer would say "Hmm - low battery".


-- Lawrence Lile

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