I have a LiIon Battery Charger IC which will draw around 50µA when not needed, see circuit 1. This is a lot of current for no work in my opinion. Now I search for a solution how I can disconnect the charger if not needed. There is one open drain status pin from the charger I can use for it (active low).
What I came up with is in circuit 2. If the Charger is loading the battery the #CHG pin is pulled down and opens the PMOS (controlled by the charger control inside the charger). If the charger is not charging the charger control is giving out a undefined voltage as I understood.
So my Question is: Can this solution do the job of disconnection the charger if not needed and connect it if needed?
Circuit 1:
Circuit 2:
Best Answer
It has 'problems'.
All readily available MOSFETS have a reverse polarity "body diode" from drain to source. In the case of a P Channel FET connected as shown, the body diode will conduct when Vdrain is more positive than Vsource. Alas, this is the situation that occurs in your circuit when the charger has power removed.
One solution is to use series connected opposite polarity MOSFETs with the sources connected and the gates connected. This arrangement is often used in LiIon cell protection circuits.
10 uA drain is 8765 hours/year x 10 uA = 88 mAh/year
= ~ 1.7 mAh/week