The bq2003 Fast Charge IC provides comprehensive fast charge control functions together with high-speed switching power control circuitry on a monolithic CMOS device. Integration of closed-loop current control circuitry allows the bq2003 to be the basis of a cost-effective solution for stand-alone and system-integrated chargers for batteries of one or more cells. Switch-activated discharge-before-charge allows bq2003-based chargers to support battery conditioning and capacity determination. High-efficiency power conversion is accomplished using the bq2003 as a hysteretic PWM controller for switch-mode regulation of the charging current. The bq2003 may alternatively be used to gate an externally regulated charging current. Fast charge may begin on application of the charging supply, replacement of the battery, or switch depression. For safety, fast charge is inhibited unless/until the battery temperature and voltage are within configured limits. Temperature, voltage, and time are monitored throughout fast charge. Fast charge is terminated by any of the following: Rate of temperature rise (T/t) Negative delta voltage (-V) Maximum voltage Maximum temperature Maximum time After fast charge, an optional top-off phase is available. Constant-current maintenence charge is provided by an external trickle resistor.