This application report describes a smart-battery charger reference design with a wide-input-voltage range. The reference design implements the System Management Bus (SMBus) protocol for communication between the MSP430 microcontroller and a SMBus-compatible battery fuel gauge. The MSP430 device interrogates the fuel gauge for voltage, current, and other parameters via SMBus. It then adjusts the pulse width modulation (PWM) duty-cycle output signals being fed to the DC/DC converter to deliver the power requested by the battery.