LP3945 Datasheet, PDF (1/15 Pages) National Semiconductor (TI) – 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 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 I²C interface (LP3945 only) — programmable charge
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
n 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_A = 25˚C
Applications
n Cellular phones
n PDAs
n Digital cameras
n USB powered devices
n Programmable current sources
Typical Application Circuit
20066502
© 2003 National Semiconductor Corporation DS200665
20066501
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