The MB3874 and MB3876 are parallel 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. The IC also enable parallel charging, or charging two batteries at the same time, dramatically reducing the charging time.