LP28013

LP28013 – 01

Aug-2017

www.lowpowersemi.com

Page 6 of 7

Automatic Recharge

Once the charge cycle is terminated, the LP28013

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.

Enable Function

The LP28013 features an enable/disable function. An input

“Low” signal at EN pin or if this pin is floating will enable the IC.

To assure the charger will switch on, the EN turn on control

level must below 0.4 volts. The charger IC r will go into the

shutdown mode when the voltage on the EN pin is greater

than 2.4 volts. If the enable function is not needed in a specific

application, it may be tied to GND or floating to keep the

charge IC in a continuously on state.

Charge Status Indicator (CHAG & PG)

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

impedance path to ground.

CHRG has two different states: strong pull-down (~5mA) and

high impedance. The strong pull-down state indicates that the

LP28013 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

LP28013 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.

Function

CHRG

Charging

Low

Charge END

High

Function

PG

VIN<UVLO

High

UVLO<VIN<OVP

Low

OVP<VIN

High

Thermal Limiting

An internal thermal feedback loop reduces the I SET rammed

charge current if the die temperature attempts to rise above a

preset value of approximately 125°C. This feature protects the

LP28013 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 LP28013. 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.

Power Dissipation

The conditions that cause the LP28013 to reduce charge

current through thermal feedback can be approximated by

considering the power dissipated in the IC. Nearly all of this

power dissipation is generated by the internal MOSFET

calculated to be approximately:

where PD is the power dissipated, VIN is the input supply

voltage, VBAT is the battery voltage and IBAT is the charge

current. The approximate ambient temperature at which the

thermal feedback begins to protect the IC is: