Lauw Lim Un Tung wrote:
>
> hi all,
> I want to backup SRAM6264 and RTC, but I fail to keep my data for a long
> time. After I checked, the battery voltage was drop below 2 volt in 2 days.
> etc.

I would strongly recommend the use of one of the commercialy available
chips for this purpose. They use lithium cells or ni-cads and provide
the proper switching of the write pulses during power down, a necessary
feature missing from your design. It's almost impossible to beat the
economics of their use. Check out Dallas or Maxim.

Tom Rogers VP - R&D Time Tech, Inc.