LP28019B

LP28019B – 01

Aug-2017

www.lowpowersemi.com

Page 6 of 7

Thermal Limiting

programmed charge current if the die temperature attempts to

rise above a preset value of approximately 125°C. This

feature protects the LP28019B 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

LP28019B. 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 LP28019B 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:

Example: An LP28019B operating from a 5V USB supply is

programmed to supply 1000mA 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 LP28019B will begin to

reduce the charge current is approximately:

The LP28019B can be used above 60℃ ambient, but the

charge current will be reduced from 1000mA. The

approximate current at a given ambient temperature can be

approximated by: