LM3621

Single Cell Lithium-Ion Battery Charger Controller

General Description

The LM3621 is a full function constant voltage, constant cur-

rent (CVCC) lithium-ion (Li+) battery charger controller. It

provides 1% regulation accuracy over the specified tempera-

ture range without requiring the use of external precision re-

sistors. The IC controls five charge modes: conditioning,

fast, top-off, monitor and maintenance. In addition, the

LM3621 detects and flags defective batteries as well as over

current and over voltage fault events. The architecture of the

IC is based on high gain constant voltage and constant cur-

rent control loops.

The LM3621 is designed to control a switching charger, a lin-

ear charger or an off-line ac adapter charger.

The LM3621 consists of a logic controller, precision bandgap

reference, wide bandwidth transconductance error amplifi-

ers, comparators, and an output buffer. The LM3621 is avail-

able in a 16-pin SOIC package and is specified over the

range of 0˚C to 70˚C.

Key Specifications

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Two selectable output voltages (4.2V or 4.1V)

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Less than 1 µA current drain from fully charged battery

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Preconditioning severely discharged cells (0V to 2.55V)

Features

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Automatic end-of-charge control

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Preset or user adjustable charge current regulation

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LED drivers for charging status and fault indication

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Battery self-discharge refresh (maintenance)

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Overvoltage/overcurrent fault detection and protection

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Defective battery pack detection

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Charge current boost control for cellular phone

applications

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Charge interruption control input

Applications

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Complete, full function, protected battery charger for

coke or graphite anode, single cell Lithium-Ion battery

packs

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Linear voltage regulator controlled chargers

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High efficiency switching regulator controlled chargers

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Cost effective wall adapter chargers

Typical Application

DS100107-7

1A, 4.1V CVCC Linear Charger for Graphite Anode Lithium-Ion Battery

March 1998

© 1998 National Semiconductor Corporation

DS100107

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