LX2203A データシートの表示（PDF） - Microsemi Corporation

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LX2203A

Li-Ion Battery Charger

Microsemi Corporation 

LX2203A

TM

®

Li-Ion Battery Charger

PRODUCTION DATA SHEET

APPLICATION NOTE

GENERAL DESCRIPTION

The LX2203A is designed to charge a single cell Lithium

Ion (Li-ion) battery using two modes: a constant current

mode, where the charge current is held constant and the

battery terminal voltage rises to 4.2V; this is followed by

constant voltage mode, where the battery voltage is held at

4.2V and the charge current starts to taper off. Once the taper

current reaches the charge termination current level the

charge cycle is ended and the STAT indicator turns off. If

the fully charged battery terminal voltage drops to 4.07V, the

battery charge cycle will be restarted.

PROTECTION FEATURES

Conditioning Current Mode – If the battery terminal

voltage is less than 2.65V, the battery charger will reduce the

charge current to 5%. This also protects the appliance from

overheating by trying to drive the full charging current into a

damaged battery.

Under Voltage Lockout – The charge cycle will not start

until the VIN voltage rises above 4.2V. Hysteresis prevents

chattering on and off.

Thermal Control loop – If the power dissipation of the

charger becomes excessive, the charge current will be

reduced to prevent the die temperature from getting above

150°C. This does not cause the charge cycle to stop.

Reverse current blocking – If VIN is grounded, current

will not flow from the battery through the charger. No

external blocking diode is required on the input.

Sleep Mode – If the EN pin is logic low or if VIN is

removed, the charger enters a sleep mode where a very low

quiescent current prevents drain from the battery.

LAYOUT GUIDELINES

• It is important when laying out the LX2203A to place

10µF ceramic capacitors close to the VIN and VBAT IC

terminals to filter switching transients.

• It is important to provide a low thermal impedance

path from the thermal pad on the bottom of the LX2203A

package to the ground plane of the circuit board to maximize

the heat dissipation. To minimize charge time it is best not to

rely on the thermal control feature as this feature will extend

the charging time when activated.

TERMINATION CURRENT PROGRAMMING

The charge termination current (or minimum taper

current) is set by selecting a value for the CTP resistor using

the following formula:

7500

R CTP =

I TERM

For example, for a termination current of 50mA set RCTP

= 150k. This formula applies to termination currents

ranging from 20mA to 500mA.

It is possible to change the termination current to different

levels for different charge rates. For a “quick charge”, the

termination current can be set to about 50% of the constant

current level; this charges the battery to about 75% capacity.

For a full charge (taking several hours) the termination

current can be set to 5% of the constant current level. The

circuit below allows switching between the two levels:

CTP

16.5k

150k

Quick/Slow

Figure 5 – 500mA or 50mA termination current

CONSTANT CHARGE CURRENT PROGRAMMING

The charge current during the constant current charge

mode is programmable by controlling the current flowing

from the CCP pin. A graph showing this relationship is

included in this specification. The CCP pin is regulated to

1.25V when the charger is active. Connecting a resistor from

the CTP to ground will produce a CTP current of:

1.25

ICTP =

R CCP

(Continued on next page)

Copyright © 2004

Rev. 1.0a, 2005-10-21

Microsemi

Integrated Products Division

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 8

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