The MB3875 and MB3877 are charging DC/DC converter ICs suitable for down-conversion, which uses pulse width modulation (PWM) for controlling the output voltage and current independently. These ICs can dynamically control the secondary battery's charge current by detecting a voltage drop in an AC adapter in order to keep its power constant (dynamically-controlled charging). The charging method enables quick charging, for example, with the AC adapter during operation of a notebook PC. With an on-chip output voltage setting resistor which allows the output voltage to be set at high precision, these ICs are best suited as internal battery chargers for notebook PCs. The MB3875 and MB3877 support 3-cell and 4-cell batteries, respectively.