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vikas
07-31-2009, 02:22 PM
Hi

Does anyone know of any battery backup circuit using the CR2032. There are IC's available but we are looking for something available off the shelf in India.

We want to keep the SRAM of a chip alive , so we need power is off.

Its not a charging type circuit.But a simple battery backup system which switches when power is lost and the ship goes into standby consuming minimal current.

Regards

vikas
08-01-2009, 10:31 AM
It was solved guys by using two diodes , IN4007.

http://worldtechnical.blogspot.com/2008/10/steering-diode-tutorial-19.html

Simple and effective :) .

docel
08-02-2009, 08:34 AM
Ahh......so many queries nowadays Vikas!!! :lol:

This solution is fine, if the chip works at 2.3V.

A single 2032 is 3V and the series diode swallows .7v

MohitM
08-02-2009, 12:48 PM
A germanium diode then, maybe? Or a schottky?

docel
08-02-2009, 09:12 PM
-MohitM :
Its ok if the Memory device operates down to 2.2v. ( and current in uA)
If not, a 2x2032 in series with the shown series diode will work.

Usually a Schottky diode is used since germanium diodes are obsolete. The backup is not that simple and calls for elaborate circuitry to prevent brownouts. There are specific backup managing ICs for a guaranteed memory retention.

A lot of backup circuits nowadays use Supercaps or Gold caps ....varyng from .47F to 10F. Infact, these supercaps have replaced batteries altogether in many consumer/proffessional devices.

vikas
08-03-2009, 04:05 AM
Hi

Though we did not face any brown outs and the sram is working fine. The voltage is not really the recommended voltage for the chip.

But i think we will shift to shottkey diodes to have the correct setup. Any commonly available ones u recommend ?

Also we did try finding a chip based solution, but after some testing with the diode method are not really seeing any advantage for going for that solution.

lhx
11-17-2009, 11:19 PM
1N5819 / 1N5822 - 1A/3A 40V Schottky diode.
These are widely used and easily available in market. The drop is about 0.2 to 0.4V

vikas
11-18-2009, 09:13 AM
Yep the Schottky diodes had done the trick.