Abstract: A battery charger IC for controlling operation of a buck converter circuit that includes a series switch and a resistor for sensing battery charging current. The battery charger IC includes a pulse-width-modulation switch drive circuit that, during charging of the battery, supplies to the buck converter circuit with an electrical signal which repeatedly turns-on and then turns-off the series switch. The battery charger IC also includes a charging-current sense amplifier which receives from the current-sensing resistor and amplifies an electrical signal which represents the battery charging electrical current. The charging-current sense amplifier includes a bridge circuit to which is coupled the electrical signal received by the charging-current sense amplifier from the current-sensing resistor and an auto-zero circuit.

Abstract: A controller for a smart battery selector included in a portable device has a plurality of switch-drivers at least equal to a plurality of smart batteries. The batteries provide battery-state data via a bus to a host computer included in the portable device. Each switch-driver effects selection of an associated battery. A control electronic-circuit in the controller directs operation of the switch-drivers for selecting the battery so that at any instant only one battery powers the portable device. A bus-snooper circuit permits the controller to independently monitor the bus for battery-condition alarm-messages. The controller may respond to such messages by selecting a different battery. The controller may also select a single battery for recharging, and may terminate charging upon receiving a battery overcharge message.