Re: Diodes for Li coin cell protection

From: Sprow (news_at_sprow.co.uk)
Date: 02/07/05 

Date: Mon, 07 Feb 2005 21:39:49 GMT

In article <1107634312.519313.206040@f14g2000cwb.googlegroups.com>,
   rickman <gnuarm@arius.com> wrote:
> I had to look pretty hard to find a small, inexpensive diode pair to
> allow an RTC to be powered by both a Li coin cell and the power rail.

[snip]

> Diodes are the right idea, but primary Li cells have a very low
> tolerance for reverse current (charging). It seems that reverse
> current builds up a layer inside that reduces the capacity of the cell.

Why not use a few diodes in series? Say, a couple of BAV99's if you can
tolerate the forward voltage drop at currents of interest, else schottky,
Sprow.