Help with battery backup circuit for LPC2378 RTC

Development Boards MicroMod
1

Hi Guys,

I am trying to design a rechargable coin cell battery backup circuit for VBAT in ARM LPC2378.

Can some one please explain how to design a circuit to provide coin cell battery backup with recharging for the coin cell. I am also considering using a super cap as alternative for battery.

Thanks in advance

tama

2

Guys some help would be appreciated.

3

There are some reference designs among the application notes for this or a similar processor, or one of the many outboard RTC clock chips.

Have you done searches for these at NXP’s website? Or Dallas/Maxim for RTC chips?

Perhaps VBAT is merely tied to a battery which is not allowed to discharge below 1.6V by use of an I-meter circuit. So the clock will work but the CPU cannot be started up with a low battery.

4

Thanks Stevech,

Thanks for your pointers. I found some circuits on Dallas website.