The LTC1731EMS8-8.4#PBF from Analog Devices is a Li-ion Linear Battery Charger Controller that has been designed to provide constant current or voltage supply for 2-cell Lithium ion (Li-ion) batteries. It requires an input voltage of 8.8 - 12 V and provides an output voltage of 8.4 V. This battery management IC (BMIC) consists of a charge control logic, error amplifiers, MOSFETs, diode, switch, current sources, and resistors. It programs the charge current using the program and sense resistor, and uses a current amplifier to serve the gate of the external P-channel MOSFET to force the same voltage drop across the sense resistor which sets the charge current. This charge controller begins charging when the potential at the supply pin (VCC) rises above the under-voltage lockout (UVLO) level and at the beginning of the charge cycle, if the battery voltage is below 4.95 V, the IC enters into the trickle charge mode. It reduces the charge current when the battery approaches the final float voltage and when the current drops to 10% of the full-scale value, an internal comparator turns OFF the N-channel MOSFET and connects a weak current source to ground, which indicates near end-of-charge (C/10) condition.

This BMIC goes into sleep mode when the input voltage is not present, which drops the charging current to 15 µA, greatly reducing the level of current drain on the battery and extending the standby time. It is also equipped with built-in UVLO (along with hysteresis) and shutdown protection circuitries for safety and reliability. This controller IC is available in a surface-mount package that measures 4.801 x 5.791 mm and is ideal for programmable current sources, charging docks and cradles, handheld computers, and cellular mobile applications.