On Apr 8, 2:12*am, Bob Larter wrote:
Franc Zabkar wrote:
On Mon, 6 Apr 2009 05:45:54 -0700 (PDT), Fox put
finger to keyboard and composed:
http://www.panasonic.com/industrial/...pdf/Panasonic_....
[...]

It gives a rough idea of the maximum allowable reverse current
depending on the application.

The examples in that document cite a reverse current of 4nA for a
Schottky diode and 6nA for a silicon diode.

But ...

A 1A 1N4001 diode has a typical reverse current of 50nA at 25degC:
http://www.onsemi.com/pub_link/Collateral/1N4001-D.PDF

A 1A 1N5817 Schottky diode has a reverse current of 1mA at 25degC:
http://www.onsemi.com/pub_link/Collateral/1N5817-D.PDF

The above leakages are measured at the rated reverse voltage, so at 2V
(5V - 3V) they would probably be a lot less. Nevertheless the figures
still suggest that Schottky diodes have worse leakage characteristics
than regular silicon diodes.

Interesting. I hadn't realised that 1N5817s were as leaky as that. The
OP should probably try to find a low reverse-leakage Schottky, or
substitute a standard diode & accept that the battery life will be
shortened due to the lowered memory voltage.

--
* * W
* . | ,. w , * "Some people are alive only because
* *\|/ *\|/ * * it is illegal to kill them." * *Perna condita delenda est
---^----^---------------------------------------------------------------

I found a compromise. A .7V 0.5 uA IR silicon diode with a 3.6V
lithium battery. I had a bunch of both lying around in my parts box.