APL3201 View Datasheet(PDF) - Anpec Electronics

Part Name

Description

Manufacturer

APL3201

Li+ Battery Charger with Thermal Regulation

Anpec Electronics 

APL3201

Function Description

Precharge Current

When the APL3201 is powered with a battery connected,

the IC first detects if the cell voltage is ready for full charge

current. If the cell voltage is less than the prequal level

(3V typ), the battery is precharged with a 55mA current

until the cell reaches the proper level. The full charging

current, as set by ISET pin, is then applied.

Charging Current Setting

The charge current is programmed by using a resistor

from the ISET pin to the ground. The battery charge cur-

rent is 1000 times the current out of the ISET pin. The

battery charge current is calculated by the following

equation:

ICHG =KSET x VSET / RSET

Where

VSET is ISET regulation voltage (nominal=1V).

K is the charging current set factor (nominal=1000).

SET

The charging current set factor and the ISET regulation

voltage are shown in the Electrical Characteristics. The

ISET regulation voltage is reduced by thermal regulation

function.

Enable (EN)

The enable input, EN, switches the charging of APL3201

on or off. With EN high, the APL3201 can begin charging.

When EN is low, charging stops, REF is shutdown, and

STAT1 and STAT2 outputs are off (high).

Battery Full Indication

Charge-done occurs when ICHG falls to 12.5% of the current

set by RSET and the charger is in voltage mode (VBATT near

4.2V). After the APL3201 enunciates the charge-done

signal, it keeps operating in voltage mode without turning

off the charger. The STAT1 is turned off (high) and STAT2

is turned on (low) when the charger is into charge-done

state.

Thermal Regulation

On-chip thermal limiting in the APL3201 simplifies PC

board layout and allows charging rates to be automatically

optimized without constraints imposed by worst-case

minimum battery voltage, maximum input voltage, and

maximum ambient temperature. When the APL3201

thermal limit is reached, the charger does not shut down

but simply reduces charging current. This allows the

board design to be optimized for compact size and typical

thermal conditions. The APL3201 reduces charging

current to keep its die temperature below +120°C. The

APL3201’s DFN3x3-10 package includes a bottom metal

plate that reduces thermal resistance between the die

and the PC board. The external pad should be soldered

to a large ground plane. This helps dissipate power and

keeps the die temperature below the thermal limit. The

APL3201’s thermal regulator is set for a +120°C die

temperature.

External Thermistor Monitor (THRM)

The APL3201 features an internal window comparator to

monitor battery pack temperature or ambient temperature

with an external negative temperature coefficient

thermistor. In typical systems, temperature is monitored

to prevent charging at ambient temperature extremes

(below 0°C or above +50°C). When the temperature

moves outside these limits, charging is stopped. If the

VTHRM returns to within its normal window, charging

resumes. Connect THRM to GND when not using this

feature. Note that the temperature monitor at THRM en-

tirely separates from the on-chip temperature limiting dis-

cussed in the Thermal Regulation section. The input

thresholds for the THRM input are 0.74 x VREF for the COLD

trip point and 0.29 x VREF for the HOT trip point.

REF

10kΩ

Thermistor

10kΩ at +25°C

THRM

100mV

TCOLD

To Regulator

THOT

FFigure 1. Thermistor Sensing Block Diagram

Copyright © ANPEC Electronics Corp.

9

Rev. A.4 - Mar., 2009

www.anpec.com.tw

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