A charge-pump biased battery protection circuit provides improved
efficiency, reduced power dissipation, and reduced complexity in battery
powered circuits. A charge pump is utilized to bias the gate of a single
pass transistor such that the voltage between the pass transistor gate
and the drain/source terminals of the pass transistor have a magnitude
greater than the battery voltage, reducing the voltage drop across the
pass transistor. The charge pump may be controlled in conformity with a
sensed current through the pass transistor, so that at times of lower
current loads, power is conserved. The bulk (body) of the pass transistor
can be controlled using a resistor coupling a battery terminal to the
bulk and a single switch coupling the bulk to a charger/load connection
terminal, permitting a single pass transistor to be used for charging and
discharging.