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

Tight output voltage accuracy (

0.5% at T

= 25°C)

Two selectable output voltages (4.2V or 4.1V)

Less than 1 µA current drain from fully charged battery

Preconditioning severely discharged cells (0V to 2.55V)

Features

Automatic end-of-charge control

Preset or user adjustable charge current regulation

LED drivers for charging status and fault indication

Battery self-discharge refresh (maintenance)

Overvoltage/overcurrent fault detection and protection

Defective battery pack detection

Charge current boost control for cellular phone
applications

Charge interruption control input

Applications

Complete, full function, protected battery charger for
coke or graphite anode, single cell Lithium-Ion battery
packs

Linear voltage regulator controlled chargers

High efficiency switching regulator controlled chargers

Cost effective wall adapter chargers

Typical Application

DS100107-7

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

March 1998

LM3621

Single

Cell

Lithium-Ion

Battery

Charger

Controller

DS100107

www.national.com

Connection Diagram

Pin Description

Pin No.

Symbol

I/O

Description

BAT

Battery pack high side sense input.

BAT

Battery pack low side sense input.

CSR

Current Sense Resistor high side input.

PFD

Pass FET gate Drive output. (N-channel).

COMP

Compensation pin for current regulation loop.

MCO

Modulation Control Output- analog control signal output

COMP

Compensation pin for voltage regulation loop.

SET

Charge current adjust input pin (see application section).

SET

Charge termination voltage control input (V

SET

= HI for 4.2V or

SET

= LO for 4.1V).

LED1

LED driver #1 output (open drain).

LED2

LED driver #2 output (open drain).

ChgInt

Charge current interrupt (active LO).

Enable

Enable charge cycle control.

Boost

Maximum output current boost control (max output current
increased by 80%).

IC common.

IC power supply.

16-Lead SOIC

DS100107-18

Top View

Order Number LM3621M or LM3621M-3.0

NSC Package Number M16A

www.national.com

Absolute Maximum Ratings

(Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Supply Voltage, V

6.0V

All pins

-0.3 V

+0.3V

Power Dissipation

100 mV

ESD Susceptibility (Note 2)

2kV

Junction Temperature

150°C

Storage Temperature

-65°C to +150°C

Lead Temperature,
soldering

Vapor Phase (60 sec)

+215°C

Infrared (15 sec)

+220°C

Operating Ratings

Ambient Temperature Range

0°C

70°C

Supply Voltage Range (Note 3)

3.0V

5.5V

Electrical Characteristics

= 4.2V unless otherwise specified. Specifications with standard type face are for T

= 25°C, and those with boldface type

apply over full operating temperature range.

Symbol

Parameter

Conditions

Min

Typ

Max

Units

OUT

Battery Regulation Voltage (Note
4)

Charge termination voltage for
V

SET

= HI

4.18

4.2

4.22

4.16

4.24

Charge termination voltage for
V

SET

=LO

4.08

4.1

4.12

4.06

4.14

Battery conditioning (Hi-Z) charge
mode, LM3621M-3.0

2.95

3.1

3.25

Battery conditioning (Hi-Z) charge
mode, LM3621M

4.05

4.1

4.15

Monitor Mode float voltage for
V

SET

= HI

4.05

4.09

4.13

Monitor Mode float voltage for
V

SET

= LO

3.80

3.85

3.90

CSR

Charge Current Regulation
Voltage (Notes 5, 16)

Fast Charge Mode

0.475

0.5

0.525

Conditioning (Hi-Z) Charge Mode

0.04

0.05

0.06

Boost Mode

0.855

0.9

0.945

BAT

-Det

Battery Voltage Detection
Threshold (Note 6)

Overvoltage Fault Threshold for
V

SET

= HI

4.28

4.40

4.50

Overvoltage Fault Threshold for
V

SET

= LO

4.18

4.30

4.40

Battery Resistance Free Voltage
Threshold

3.55

3.65

3.75

Conditioning (Hi-Z) Charge Mode
Threshold

2.45

2.55

2.65

2.40

2.70

CSR

-Det

Charge Current Voltage Detection
Threshold (Notes 7, 16)

End of charge threshold

Over Current Fault Threshold

0.95

1.05

Quiescent Current

Standby Mode with I

OUT

= 0 mA

OUT

MCO Output Source Current

MCO

= 1.0V

MCO

Maximum MCO Output Voltage

OUT

= 1 mA, V

= 5.5V

4.9

OUT

= 1 mA, V

= 3.0V

2.9

GM-V

V-Reg Loop Error Amp
Transconductance

0.1

mA/V

SLEW

-V

V-Reg Loop Error Amp Slew
Current

100

µA

GM-I

I-Reg Loop Error Amp
Transconductance

mA/V

SLEW

-I

I-Reg Loop Error Amp Slew
Current

200

µA

1 Hour Timer

min

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Electrical Characteristics

(Continued)

= 4.2V unless otherwise specified. Specifications with standard type face are for T

= 25°C, and those with boldface type

apply over full operating temperature range.

Symbol

Parameter

Conditions

Min

Typ

Max

Units

LKG

-0

Battery Load Current (Note 8)

= 0V

µA

LKG

-MM

Battery Load Current (Note 9)

Monitor Mode

µA

BSD

Maximum Allowed Battery Self-
Discharge(Note 10)

SET

= HI

110

150

SET

= LO

220

260

300

CSR

Fast Charge Current Regulation
Adjustment Transfer Ratio (Notes
11, 12)

ISET

= 0.5V

0.90

0.93

0.96

V/V

LED

LED1 & LED2 Driver Sink Current

LED1

= V

LED2

= 1.5V

SUV

Start Up Voltage (Note 13)

3.4

UVR

Under Voltage Reset (Note 14)

2.2

PFD

-MAX

Maximum PFD Output Drive

no DC load on PFD

-0.2

PFD

-MIN

Minimum PFD Output Drive

no DC load on PFD

+0.1

Logic Input Low (Note 15)

0.5

Logic Input High (Note 15)

-0.5

DIG

Digital Input Leakage Current
(Note 15)

-1

µA

Note 1: Absolute Maximum Ratings indicates limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device is in-
tended to be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see
the Electrical Characteristics.

Note 2: ESD rating is based on the human body model, 100 pF discharged through 1.5 k

Note 3: LM3621 requires a minimum V

of 3.4V to start-up. After start-up, the operating range is 3.0V to 5.5V.

Note 4: V

OUT

is measured between V

BAT

+ and CSR.

Note 5: V

CSR

is measured between CSR and V

(across the current sense resistor).

Note 6: V

BAT

-Det is measured between V

BAT

+ and V

BAT

Note 7: V

CSR

-Det is measured between CSR and V

(across the current sense resistor).

Note 8: This is the current drawn from the battery by the LM3621 when V

= 0V.

Note 9: This is the current drawn from the battery by the LM3621 when the charger is in Monitor Mode.

Note 10: This is the maximum battery voltage droop that is allowed before the charger initiates a fast charge mode to refresh the battery to its full charge capacity.

Note 11: The current regulation and detection levels can be set by applying a dc voltage adjusting between 0.1V to 1V to the I

SET

pin without changing the value

of the current sense resistor. To ensure proper operation, if the default current regulation and detection values are desired, then a capacitor of at least 100 pF should
be connected from I

SET

to V

(GND).

Note 12: Transfer ratio of V

CSR

ISET

to adjust the fast charge current regulation level. See application section.

Note 13: Minimum V

supply voltage required at start-up.

Note 14: The LM3621 goes to a shutdown or reset state during "brown out" (i.e., when V

UVR

)

Note 15: Digital inputs are Enable, Boost, Chgint and V

SET

. To ensure proper operation, never allow any unused input pin to be left open.

Note 16: No external voltage applied to I

set

pin; a 100 pF capacitor is connected across I

set

and V

Definition of Terms

OUT

: Voltage measured between V

BAT

+ and CSR.

CSR

: Charging current sense voltage measured between

CSR and V

(Gnd).

BATTERY

: Battery terminal voltage measured between

BAT

+ and V

BAT

ESR: The equivalent series resistance of a battery. The ESR
is the purely resistive component of a battery's impedance.
Its value is usually determined by the battery construction.

RFV: The RFV (resistance free voltage, often called the float
voltage) is the open circuit terminal voltage of a battery
which is free from the ESR voltage drop error.

SET

: External voltage applied to I

SET

pin, measured be-

tween I

SET

and V

, to override the default value of V

CSR

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