LP4074-00

Aug.-2018

www.lowpowersemi.com

Page 5 of 8

Preliminary Datasheet

LP4074

Applications Information

The LP4074 is a single cell lithium-ion battery charger using a

constant-current/constant-voltage algorithm. It can deliver up

to 600mA of charge current (using a good thermal PCB layout)

with a final float voltage accuracy of ± 1%. The LP4074

includes an internal P-channel power MOSFET and thermal

regulation circuitry. No blocking diode or external current

sense resistor is required; thus, the basic charger circuit

requires only three external components. Furthermore, the

LP4074 is capable of operating from a USB power source.

Normal Charge Cycle

A charge cycle begins when the voltage at the VIN pin rises

above the UVLO threshold level and a 1% program resistor is

connected from the ISET pin to ground or when a battery is

connected to the charger output. If the BAT pin is less than

2.9V, the charger enters trickle charge mode.

When the BAT pin voltage rises above 2.9V, the charger

enters constant-current mode, where the programmed charge

current is supplied to the battery. When the BAT pin

approaches the final float voltage (4.2V), the LP4074 enters

constant-voltage mode and the charge current begins to

decrease. When the charge current drops to 1.5/10 of the

programmed value the charge cycle ends.

Programming Charge Current

The charge current is programmed using a single resistor

from the ISET pin to ground. The battery charge current is

1000 times the current out of the ISET pin. The program

resistor and the charge current are calculated using the

following equations:

The charge current out of the BAT pin can be determined at

any time by monitoring the ISET pin voltage using the

following equation:

Charge Status Indicator (CHRG)

The charge status output has two different states: strong

pull-down (~5mA) and high impedance. The strong pull-down

state indicates that the LP4074 is in a charge cycle. High

impedance indicates that the charge cycle complete or the

than 150mV above the BAT pin voltage or insufficient voltage

is applied to the VIN pin. A microprocessor can be used to

distinguish between these two states.

Charge Stage

STAT1 Status

STAT2 Status

Charging

Low

High

Charge Complete

High

Low

Charge Termination

A charge cycle is terminated when the charge current falls to

1.5/10th the programmed value after the final float voltage is

reached. This condition is detected by using an internal,

filtered comparator to monitor the ISET pin. When the ISET

1ms), charging is terminated. The charge current is latched off

and the LP4074 enters standby mode, where the input supply

current drops to 50µA. When charging, transient loads on the

BAT pin can cause the ISET pin to fall below 150mV for short

periods of time before the DC charge current has dropped to

the termination comparator ensures that transient loads of this

nature do not result in premature charge cycle termination.

Once the average charge current drops below 1.5/10th the

programmed value, the LP4074 terminates the charge cycle

and ceases to provide any current through the BAT pin. In this

state, all loads on the BAT pin must be supplied by the battery.

The LP4074 constantly monitors the BAT pin voltage in

standby mode. If this voltage drops below the 4.0V recharge

is once again supplied to the battery. To manually restart a

charge cycle when in standby mode, the input voltage must

be removed and reapplied.