Preliminary

LP4054

LP4054-datasheet V1.0

Sep.-2006

3-3

Functional Pin Description

PIN

LP4054

DESCRIPTION

CHRG

1

Open-Drain Status Output

GND

2

Ground

BAT

3

Charge Current Output

VCC

4

Positive Input Supply Voltage

PROG

5

Charge Current Program, Charge Current Monitor and

Shutdown Pin.

Pin Functions

CHRG (PIN 1):

Open-Drain Charge Status Output. When the battery is charging, the CHRG pin is pulled low by an internal

N-channel MOSFET. When the charge cycle is completed, a weak pull-down of approximately 12µA is connected to

the CHRG pin, indicating a “AC present” condition. When the LP4054 detects an undervoltage lockout condition,

CHRG is forced high impedance.

GND (PIN 2): Ground.

BAT (PIN 3):

Charge Current Output. Provides charge current to the battery and regulates the final float voltage to 4.2V. An

internal precision resistor divider from this pin sets the float voltage which is disconnected in shutdown mode.

VCC (PIN 4): Positive Input Supply Voltage. Provides power to the charger. VCC can range from 4.35V to 6.5V and

should be bypassed with at least a 1µF capacitor. When VCC drops to within 30mV of the BAT pin voltage, the

LP4054 enters shutdown mode, dropping IBAT to less than 2µA.

PROG (PIN 5): Charge Current Program, Charge Current Monitor and Shutdown Pin. The charge current is

programmed by connecting a 1% resistor, RPROG, to ground. When charging in constant-current mode, this pin servos

to 1V. In all modes, the voltage on this pin can be used to measure the charge current using the following formula:

The PROG pin can also be used to shutdown the charger. Disconnecting the program resistor from ground allows a

3µA current to pull the PROG pin high. When it reaches the 1.94V shutdown threshold voltage, the charger enters

shutdown mode, charging stops and the input supply current drops to 25µA. This pin is also clamped to

approximately 2.4V. Driving this pin to voltages beyond the clamp voltage will draw currents as high as1.5mA.

Reconnecting RPROG to ground will return the charger to normal operation.

LP4054

(TSOT23-5)