The MAX781 generates +3.3V with high efficiency through synchronous rectification and PWM operation at heavy loads. It uses Idle ModeTM operation at light loads. Only small external components are required because of the device's high switching frequency (300kHz) and advanced current-mode PWM architecture that allows for output capacitance as low as 50F per ampere of load. The MAX781 is configured by 32 bits of serial data. These bits select the operating mode, set the switch-mode battery charger current level, select one of eight analog multiplexer channels, and turn on/off the five high-side gate drivers. A status byte read from the serial interface indicates if the battery has been removed, if the DC charging source has been connected, or if there is a fault condition on the +3.3V output. An interrupt output signals the CPU if a status signal changes.