LP4075-00

Aug.-2019

www.lowpowersemi.com

Page 6 of 7

Preliminary Datasheet

LP4075

Thermal Limit

An internal thermal feedback loop reduces the programmed

charge current if the die temperature attempts to rise above a

preset value of approximately 125℃. This feature protects the

LP4075 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 LP4075. 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.

Automatic Recharge

Once the charge cycle is terminated, the LP4075 continuously

monitors the voltage on the BAT pin using a comparator with

battery voltage falls below 4.0V (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.

CHRG output enters a strong pull-down state during recharge

cycles.

Power Dissipation

The conditions that cause the LP4075 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—this

is calculated to be approximately:

VIN Bypass Capacitor

Many types of capacitors can be used for input bypassing;

however, caution must be exercised when using multilayer

ceramic capacitors. Because of the self-resonant and high Q

characteristics of some types of ceramic capacitors, high

voltage transients can be generated under some start-up

conditions, such as connecting the charger input to a live

power source. Adding a 1.5Ω resistor in series with an X5R

ceramic capacitor will minimize start-up voltage transients.

Layout Considerations



For the main current paths as indicated in bold lines,

keep their traces short and wide.



Put the input capacitor as close as possible to the device

pins (VIN and GND).



Connect all analog grounds to a command node and

then connect the command node to the power ground

behind the output capacitors.