I would like to prevent the battery in a device from discharging (initially) until the usb is plugged in (to keep charge on the battery during storage and shipping). I am using a typical LiPo protection circuit (BQ2970):
I need to disable the discharge MOSFET until a USB cable is plugged in. I'm sure this has been done before, but I don't have a common reference voltage to implement any of my ideas (have USB v-divided to drive MOSFET etc.).