Preliminary Datasheet

LP28055

LP28055 – 02

Oct.-2018

www.lowpowersemi.com

Page 6 of 7

Charge Status Indicator(STAT1/STAT2)

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 LP28055 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 LP28055 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

STAT1(pin7)

STAT2(pin6)

Charging

Low

High

Charge END

High

Low

Thermal Limiting

charge current if the die temperature attempts to rise above a

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

LP28055 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 LP28055. 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 LP28056 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:

TA=125℃-PDθJA

Example: An LP28056 operating from a 5V USB supply is

programmed to supply 800mA full-scale current to a

discharged Li-Ion battery with a voltage of 3.75V. Assuming θ

JA is 65℃ / W (see Board Layout Considerations), the

ambient temperature at which the LP28056 will begin to

reduce the charge current is approximately:

The LP28056 can be used above 60℃ ambient, but the

charge current will be reduced from 800mA. The approximate

current at a given ambient temperature can be approximated

by: