LP3945

LP3945/LP3946 Battery Charge Management System October 2003 LP3945/LP3946 Battery Charge Management System General Description The LP3945 and LP3946 are complete charge management systems that safely charge and maintain a Li-Ion battery or a four-cell Ni-MH (LP3945 only) battery pack. The LP3945 offers the flexibility of programming charge current, battery regulation voltage (4.1V/4.2V), battery type (Li-Ion/Ni-MH), and End Of Charge (EOC) termination through the use of I2C interface. On the LP3946, these parameters are programmed at the factory per customer specification. The pass transistor, charge current sensing resistor and charge current setting resistors are all integrated inside the LP3945 and LP3946. This eliminates the use of external components and significantly reduces design time and board space. The LP3945 and LP3946 operate in four modes: prequalification, constant current, constant voltage and maintenance modes. The LP3945 features Ni-MH charging mode as well. The charger has under-voltage and over-voltage protection as well as an internal 5.6 hr timer to prevent overcharging the battery. There are two open drain outputs for status indication. An internal amplifier readily converts the charge current into a voltage. Also, the charger can operate in an LDO mode providing up to 1 Amp to the load. Features n Integrated pass transistor n Does not require external charge current setting or sensing resistors n I2C interface (LP3945 only) — programmable charge cur...