Maxim Integrated Products has developed a stand-alone, switch-mode Li battery charger controller for use with one to four cell configurations. The device features better than 0.8% battery regulation voltage accuracy, 90% conversion efficiency and a complete state machine to safely control the charging sequence. The MAX1737 features an internal voltage regulator and allows up to 28 VDC with a duty cycle of 98%. The device regulates the voltage set point and charging current with two complimentary loops that work the transition between current regulation (fast charge) and voltage regulation (near full-charge) to optimize battery life.