LP28019B

LP28019B – 01

Aug-2017

www.lowpowersemi.com

Page 5 of 7

Application Information

Input Voltage Range

The LP28019B has built-in input voltage surge protection as

high as +28V. The charger IC will be automatically disabled

when the input voltage is lower than 4.4V or higher than 7.0V.

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

above the UVLO threshold level, when a battery is connected

to the charger output. If the BAT pin is less than 2.6V, the

charger enters trickle charge mode. In this mode, the

LP28019B

supplies

approximately

1/10

the

ISET

programmed charge current to bring the battery voltage up to

a safe level for full current charging. When the BAT pin

voltage rises above 2.6V, the charger enters constant-current

mode(CC), where the ISET programmed charge current is

supplied to the battery. When the BAT pin approaches the

final float voltage, the LP28019B enters constant-voltage

mode(CV) and the charge current begins to decrease, and the

battery full indication is set when the charge current in the CV

mode is reduced to the programmed full battery current

(1/10).

ISET programming Charge Current

connecting from the ISET pin to GND. The relationship of the

charge current and the programming resistance is established

by the following table.

1.5

1000

2

700

3.3

420

10

130

Automatic Recharge

Once the charge cycle is terminated, the LP28019B

continuously monitors the voltage on the BAT pin. A charge

cycle restarts when the battery voltage falls below 4.05V

(which corresponds to approximately 80% to 90% battery

capacity). This ensures that the battery is kept at or near a

fully charged condition and eliminates the need for periodic

charge cycle initiations.

Charge Termination

A charge cycle is terminated when the charge current falls to

1/10th the ISET 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 LP28019B constantly monitors the BAT pin voltage in

standby mode. If this voltage drops below the 4.05V 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, or the charger must be shut down

and restarted using the ISET pin.

Charge Status Indicator(CHRG)

After application of a 5V source, the input voltage rises above

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

strong pull-down state indicates that the LP28019B is in a

charge cycle. Once the charge cycle has terminated, the pin

state is determined by under voltage lockout conditions. High

impedance indicates that the LP28019B is in under voltage

lockout mode: either VIN is less than 100mV 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—this method is discussed in the Applications

Information section.

Function

CHRG

Charging

Low

Charge Finish

High