The LTC1730ES8-4.2#TRPBF from Analog Devices is a Li-ion Battery Pulse Charger that offers a complete pulse charging solution for single-cell Li-ion batteries. It requires an input voltage of 4.5 - 12 V and an input current of 2 mA. This charger consists of control logic, error amplifiers, MOSFETs (NMOS), current sources, voltage sources, and resistors. It switches ON the internal MOSFET to allow the current limited input source to provide the necessary charging current, virtually eliminating heat generation in the charger. This battery charger’s battery approaches the programmed voltage, the MOSFET begins switching between OFF and ON states with the duty cycle gradually decreasing as the battery reaches a fully-charged condition. It indicates the end-of-charge condition at the CHRG pin when the average charge current falls to C/10 of the original value.

This Li-ion charger uses an external sense resistor to limit the maximum charge current as a safety precaution against a user connecting a wall adapter with the incorrect or no current limit. It also utilizes the built-in MOSFET to prevent reverse current from flowing if the input voltage is shorted to ground, thereby eliminating the need for a separate blocking diode. This charger is available in a surface-mount package that measures 4.8 x 5.8 mm and is ideal for standalone Li-ion battery charging, handheld computers, and cellular telephone applications.