LP28303ASPF datasheet(5/8 Pages) POWER

5 / 8 page

LP28303A-00

Apr.-2017

Email: marketing@lowpowersemi.com

www.lowpowersemi.com

Page 5 of 8

Preliminary Datasheet

LP28303A

Application Information

LP28303A is a 2.5A synchronous buck Li-Ion battery

charger integrates 600KHz switching frequency and

full protection functions. The charge current up to

2.5A can be programmed by using the external

resistor for different portable applications and

indicates

the

charger

current

information

simultaneous.

In constant current mode, the charge current is set

by the external sense resistor RCS and an internal

50mV reference;

IBAT=Vcs/RCS=50mV/RCS

When

the

battery

voltage

approaches

the

programmed float voltage, the charge current will

start to decrease. When the current drops to 10% of

the full-scale charge current, an internal comparator

turns off charging is terminated

Shutdown

The LP28303A can be shut-down by pulling the NTC

pin to VIN. When the NTC pin is released, the

internal timer is reset and a new charge cycle starts.

In shutdown, the output of the CHRG pin is high

impedance. Removing the input power supply will put

the charger into sleep mode. If the voltage at the VIN

pin drops below (VBAT+200mV) or below the UVLO

level, the LP28303A goes into a low current sleep

mode, reducing the battery drain current.

Input Source Qualification

After REG amplifier powers up, the LP28303A

checks the current capability of the input source. The

input source has to meet the VIN>4.3V to enable the

chip.

Automatic Recharge

Once the charge cycle is terminated, the LP28303A

continuously monitors the voltage on the BAT pin

using a comparator with a 1.8ms filter time

RECHARGE). 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.

Inductor Selection

Operating frequency was chosen for the buck

switcher in order to minimize the size of the inductor.

However, take care to use inductors with low core

loss at this frequency. To calculate the inductor ripple

current:

Battery Temperature Detection

The LP28303A continuously monitors temperature

by measuring the voltage between the NTC and

GND pins. A negative or a positive temperature

coefficient thermistor (NTC, PTC) and an external

voltage divider typically develop this voltage. The

LP28303A compares this voltage against its internal

VNTC1 and VNTC2 thresholds to determine if charging

is allowed. The temperature sensing circuit is

immune to any fluctuation in VIN, since both the

external voltage divider and the internal thresholds

(VNTC1 and VNTC2) are referenced to VIN.

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