LP4054H datasheet(5/8 Pages) POWER

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LP4054H-00

Aug.-2018

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Preliminary Datasheet

LP4054H

Applications Information

The LP4054H 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

LP4054H 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 LP4054H 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 LP4054H 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:

RISET=1000÷IBAT,

IBAT=1000÷RISET

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

any time by monitoring the ISET pin voltage using the

following equation:

IBAT=VISET÷RISET×1000

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 LP4054H is in a charge cycle. High

impedance indicates that the charge cycle complete or the

LP4054H is in under voltage lockout mode: either VIN is less

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

pin voltage falls below 100mV for longer than TTERM (typically

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

and the LP4054H 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 1.5/10th the programmed value. The 1ms filter

time (TTERM) on 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 LP4054H

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 LP4054H constantly

monitors the BAT pin voltage in standby mode. If this voltage

drops below the 4.0V recharge threshold (VRECHRG), another

charge cycle begins and current 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.

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