The LTC1734L is a low cost, single cell, constant-current/constant-voltage Li-Ion battery charger controller. When combined with a few external components, the SOT-23 package forms a very small, low cost charger for single cell lithium-ion batteries. The LTC1734L is a lower charge current version of the LTC1734.The LTC1734L provides a fixed float voltage of 4.2V with 1% accuracy (for 4.1V and 4.15V float voltages, contact Analog Devices Marketing). Constant current is programmed using a single external resistor between the PROG pin and ground. Manual shutdown is accomplished by floating the program resistor while removing input power automatically puts the LTC1734L into a sleep mode. Both the shutdown and sleep modes drain near zero current from the battery.Charge current can be monitored via the voltage on the PROG pin allowing a microcontroller or ADC to read the current and determine when to terminate the charge cycle. The output driver is both current limited and thermally protected to prevent the LTC1734L from operating outside of safe limits. No external blocking diode is required.The LTC1734L can also function as a general purpose current source or as a current source for charging nickel-cadmium (NiCd) and nickel-metal-hydride (NiMH) batteries using external termination.Charge CurrentV floatLTC1734180mA to 700mA4.1V or 4.2VLTC1734L50mA to 180mA4.2VApplicationsCellular TelephonesHandheld ComputersDigital CamerasCharging Docks and CradlesLow Cost and Small Size ChargersProgrammable Current Sources