AVR-Chat

For production use I still would recommend using an auto-switching power
MUX.  They rock.  They will auto-sense the voltage differential and
automatically switch between sources.

Their cheap too.

TI makes a few of them.  Again, I'm using the tps2115. Here's the
datasheet:

http://focus.ti.com/lit/ds/symlink/tps2115.pdf

They use integrated MOSFETS for a low voltage drop.

Otherwise, you could use the circuits below but I would suggest using a
Schottky diode which will give you a lower voltage drop and be more
efficient.

-----Original Message-----
From: Wagner Lipnharski [mailto:wagner@ustr.net] 
Sent: Sunday, March 14, 2004 1:48 PM
Subject: Re: [AVR-Chat] back-up power supply circuit

Battery ---------->|----o----o MCU +VCC
Main 5V6         Diode  |      Main +5V, Backup +4.8V
                        |
                        |
Battery----------->|----'
Backup 5.5V      Diode

I guess simpler than that is impossible.
Does it solve your problem?

jaythesis wrote:
> hi!
> 
> does anyone have a circuit design on back-up power supply? like if
> the main power is cut-off, the battery automatically takes over to
> supply the MCU. can i have the design?
> 
> thanks in advance.
> 
> -jay

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