Is there diode with both low forward voltage(<0.2V) and low reverse current(<0.2uA)?

Question

I want to use MS621FE rechargeable lithium battery as RTC battery.

The working voltage of my circuit is 3.3V.

MS621FE allows a charge voltage from 3.1V to 3.3V.

To prevent the battery try to supply the system I need a diode series with the battery to the VDD.

The problem is,I want to charge the battery the most possibly full, and the lowest reverse current when system is powered-down, which means I need a diode with both low forward voltage(<0.2V) and low reverse current(<0.2uA), is it possible?

I found IN4148, but the forward voltage is too high, and some Schottky diode has the low enough forward voltage, but the reverse current is too high (10uA+).

Current consumption of my RTC module is only 1.4uA, I think I should find a diode whose reverse current is lower than 0.2uA to reach the minimum cost.

Thanks.

Answer 1

Not possible to have this If and low Vf, and low Ir leakage with those specs in Schottky Diodes.

best match http://www.digikey.com/product-detail/en/texas-instruments/SM74611KTTR/296-35688-2-ND/3906419

• Most likely candidate

http://www.diodes.com/_files/datasheets/B370Q-B3100Q.pdf No spec for Ir@-3V but rated for 40V

Answer 2

You could consider using a low leakage p channel MOSFET as the "diode" such as the FDN304P from Fairchild. It exhibits an on-resistance sub 100 milli ohms when on and a leakage current of no more than 100 nA when off. You will need to control the gate to make this work so I'm assuming that you have the spare IO lines to do so.