LM3641

LM3641 Lithium-Ion Battery Pack Protection Circuit January 1999 LM3641 Lithium-Ion Battery Pack Protection Circuit General Description The LM3641 Lithium Protection Integrated Circuit resides inside a 3.6V Lithium-Ion battery pack consisting of a single cell or multiple parallel cells. The IC controls the ON/OFF state of a pair of low threshold N-channel power MOSFETs placed in series with the battery cell(s). The purpose of this MOSFET pair is to protect the cell(s) from inadvertent electrical over-stress. The IC compares the cell voltage against internally programmed minimum and maximum limits. Transient voltage faults of approximately 1.25 seconds are tolerated. The IC also monitors the bi-directional current flow in the battery pack by measuring the voltage across a robust 4 mΩ current sensing resistor internal to the protection IC package. The IC turns OFF the MOSFET pair whenever any fault limit is exceeded. Momentary current surges < 4 ms are tolerated. The Enable pin allows external ON/OFF control of the MOSFET pair and resets the IC after the MOSFET pair is turned OFF and the pack is safe to operate again. The limits for overcharge and overdischarge voltage, as well as independent limits for each direction of overcurrent are factory adjusted employing EEPROM. Features n Automatic battery disconnect when the cell is over-charged or over-discharged. n Maximum cell voltage for MOSFET conduction is factory programmable between 4.0V and 4.4V with a ± 25 mV tolerance (0...