The LTC1325 provides the core of a flexible, cost-effective solution for an integrated battery management system. The monolithic CMOS chip controls the fast charging of nickel-cadmium, nickel-metal-hydride, lead-acid or lithium batteries under microprocessor control. The device features a programmable 111kHz PWM constant current source controller with built-in FET driver, 10-bit ADC, internal voltage regulator, discharge-before-charge controller, programmable battery voltage attenuator and an easy-to-use serial interface. The chip may operate in one of five modes: power shutdown, idle, discharge, charge or gas gauge. In power shutdown the supply current drops to 30A and in the idle mode, an ADC reading may be made without any switching noise affecting the accuracy of the measurement. In the discharge mode, the battery is discharged by an external transistor while the battery is being monitored by the LTC1325 for fault conditions. The charge mode is terminated by the P while monitoring any combination of battery voltage and temperature, ambient temperature and charge time. The LTC1325 also monitors the battery for fault conditions before and during charging. In the gas gauge mode the LTC1325 allows the total charge leaving the battery to be calculated.