The LTC4002-4.2 is a complete battery charger controller for single cell 4.2V lithium-ion batteries. With a 500kHz switching frequency, the LTC4002-4.2 provides a small, simple and efficient solution to fast charge Li-Ion batteries from a wide range of supply voltages. An external sense resistor sets the charge current with 5% accuracy. An internal resistor divider and precision reference set the final float voltage to 4.2V with 1% accuracy.