LP4061-02

Mar.-2017

www.lowpowersemi.com

Page 5 of 7

Preliminary Datasheet

LP4061

Application Information

The LP4061 is a single cell lithium-ion battery charger using a

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

to 800mA of charge current (using a good thermal PCB layout)

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 two external components. Furthermore, the

LP4061 is capable of operating from a USB power source.

Normal Charge Cycle

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

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

connected from the PROG 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. In this mode,

the LP4055 supplies fixed 30mA current to bring the battery

voltage up to a safe level for full current charging.

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, the LP4061 enters

constant-voltage mode and the charge current begins to

decrease. The charge cycle ends when the charge current

drops to 1/10 of the programmed value.

Programming Charge Current

The charge current is programmed using a single resistor

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

1000 times the current out of the PROG 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 PROG pin voltage using the

following equation:

Charge Termination

A charge cycle is terminated when the charge current falls to

1/10th the PROG rammed value after the final float voltage is

reached. This condition is detected by using an internal,

filtered comparator to monitor the PROG pin. When the

PROG pin voltage falls below 200mV for longer than

tTERM(typically 1ms), charging is terminated. The charge

current is latched off and the LP28056S enters standby mode,

where the input supply current drops to 200µA. In this state,

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

(Note: C/10 termination is disabled in trickle charging and

thermal limiting modes).

Charge Status Indicator (STAT)

The charge status output has two different states: strong

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

state indicates that the LP4061 is in a charge cycle. Once the

charge cycle has terminated, the pin state is determined by

under voltage lockout conditions. High impedance indicates

is less than 100mV above the BAT pin voltage or insufficient

voltage is applied to the VCC pin. A microprocessor can be

used to distinguish between these two states

Function

STAT1

STAT2

Charging

Low

High

Charge Completed

High

Low

Charge Termination

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise above a

preset value of approximately 150℃. This feature protects the

LP4061 from excessive temperature and allows the user to

push the limits of the power handling capability of a given

circuit board without risk of damaging the LP4061. The charge

current can be set according to typical (not worst-case)

ambient temperature with the assurance that the charger will

automatically reduce the current in worst-case conditions.