The UCC3956 family of switch-mode lithium-ion battery-charger controllers accurately control lithium-ion battery charging with a highly-efficient average-current-control loop. This chip is designed to work as a stand-alone charger controller for a single-cell or multiple-cell battery pack. This chip combines charge-state logic and average-current PWM control circuitry with a 14-bit counter to program the overcharge time. The charge-state logic indicates current-or voltage-control depending on the charge state. The chip includes undervoltage lockout (UVLO) circuitry to ensure sufficient supply voltage is present before output switching starts. Additional circuit blocks include a differential-current-sense amplifier, a 1% voltage reference, voltage- and current-error amplifiers, PWM latch, charge-state decode bits, and a 500-mA output driver.