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: pre-qualification, 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.
The LP3945 and LP3946 are complete charge management systems that safely charge Li‑ion batteries (and Ni‑MH for the LP3945) with programmable charge current, battery regulation voltage, and end‑of‑charge termination via an I²C interface. Integrated pass transistors, charge‑current sensing, and a built‑in 5.6‑hour timer reduce external components and improve safety.
The document includes a general description, pin description, electrical characteristics, I²C interface details, application notes, thermal performance of the leadless lead‑frame package, PCB layout recommendations, physical dimensions, and customer support information.
| Charger voltage accuracy | 1% over 0°C‑85°C |
|---|---|
| Input voltage range | 4.5 V to 6.0 V |
| Built‑in timer | 5.6 hour safety timer |
| Fast charge current range | 500 mA to 950 mA |
| End‑of‑charge current accuracy | ±10 % |
| Battery regulation voltage | 4.1 V or 4.2 V |
| LDO mode output current | up to 1 A |
The device operates with an input voltage between 4.5 V and 6.0 V.