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 I

interface. On the LP3946, these parameters are pro-

grammed 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 mainte-

nance 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

I

current, EOC current and battery regulation voltage

n

Near-depleted battery preconditioning

n

Built-in 5.6 hour timer

n

Under voltage and over voltage lockout on adaptor

n

Charge status indicators

n

Charge current monitor analog output

n

LDO mode operation can source 1 amp

n

Continuous over current/temperature protection

Key Specifications

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1% charger voltage accuracy over 0˚C

≤ T

J

≤ 85˚C

n

4.5V to 6.0V input voltage range

n

LLP package power dissipation: 2.7W at T

Applications

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Cellular phones

n

PDAs

n

Digital cameras

n

USB powered devices

n

Programmable current sources

Typical Application Circuit

20066502

20066501

October 2003

© 2003 National Semiconductor Corporation

DS200665

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