Texas Instruments BQ2002GSN, BQ2002GPN, BQ2002ESNTR, BQ2002ESN-SITR, BQ2002ESN-SI Datasheet

Features

➤

Fast charge of nickel cadmium
or nickel-metal hydride batter

-

ies

➤

Direct LED output displays
charge status

➤

Fast-charge termination by -∆V,
maximum voltage, maximum
temperature, and maximum
time

➤

Internal band-gap voltage ref

-

erence

➤ Optional top-off charge
➤ Selectable pulse trickle charge

rates

➤ Low-power mode
➤ 8-pin 300-mil DIP or 150-mil

SOIC

General Description

The bq2002E and bq2002G Fast­Charge ICs are low-cost CMOS bat

-

tery-charge controllers providing reli

­able charge termination for both NiCd
and NiMH battery applications. Con

­trolling a current-limited or co n

­stant-current supply allows the
bq2002E/G to be the basis for a cost­effective stand-alone or system-inte

­grated charger. The bq2002E/G inte

­grates fast charge with optional top-off
and pulsed- trickle control in a single
IC for charging one or more NiCd or
NiMH battery cells.

Fast charge is initiated on application
of the charging supply or battery re­placement. For safety, fast charge is
inhibited if the battery temperature
and voltage are outside configured
limits.

Fast charge is terminated by any of
the following:

n

Peak voltage detection (PVD)

n

Negative delta voltage (-∆V)

n

Maximum voltage

n

Maximum temperature

n

Maximum time

After fast charge, the bq2002E/G op

­tionally tops-off and pulse-trickles the
battery per the pre-configured limits.
Fast charge may be inhibited using
the INH pin. The bq2002E/G may
also be placed in low-standby-power
mode to reduce system power con­sumption.

The bq2002E differs from the
bq2002G only in that a slightly dif­ferent set of fast-charge and top-off
time limits is available. All differ­ences between the two ICs are illus­trated in Table1.

1

NiCd/NiMH Fast-Charge Management ICs

bq2002E/G

TM Timer mode select input
LED

Charging status output
BAT Battery voltage input
V

SS

System ground

1

PN-200201.eps

8-Pin DIP or

Narrow SOIC

2

3

4

8

7

6

5

TM

LED

BAT
V

SS

CC

INH

V

CC

TS

TS Temperature sense input
V

CC

Supply voltage input
INH Charge inhibit input
CC Charge control output

Pin Connections

Pin Names

2/99

bq2002E/G Selection Guide

Part No. LBAT TCO HTF LTF

-∆V

PVD Fast Charge t

MTO

Top-Off Maintenance

bq2002E

0.175 ∗
V

CC

0.5 ∗
V

CC

0.6 ∗
V

CC

None ✔ C/2 200 None C/32

✔ 1C 80 C/16 C/32

✔ 2C 40 None C/32

bq2002G

0.175 ∗
V

CC

0.5 ∗
V

CC

0.6 ∗
V

CC

None ✔ C/2 160 None C/32

✔ 1C 80 C/16 C/32

✔ 2C 40 None C/32

Pin Descriptions

TM

Timer mode input

A three-level input that controls the settings
for the fast charge safety timer, voltage ter

­mination mode, top-off, pulse-trickle, and
voltage hold-off time.

LED

Charging output status

Open-drain output that indicates the charging
status.

BAT

Battery input voltage

The battery voltage sense input.The input to
this pin is created by a high-impedance re

­sistor divider network connected between
the positive and negative terminals of the
battery.

V

SS

System ground

TS

Temperaturesenseinput

Input for an external battery temperature
monitoring thermistor.

V

CC

Supply voltage input

5.0V±20% power input.

INH

Charge inhibit input

When high, INH suspends the fast charge in
progress. When returned low, the IC re-

sumes operation at the point where initially
suspended.

CC

Charge control output

An open-drain output used to control the
charging current to the battery. CC switch

­ing to high impedance (Z) enables charging
current to flow, and low to inhibit charging
current. CC is modulated to provide top-off,
if enabled,andpulsetrickle.

Functional Description

Figure 2 shows a state diagram and Figure 3 shows a
block diagram of the bq2002E/G.

Battery Voltageand Temperature
Measurements

Battery voltage and temperature are monitored for
maximum allowable values. The voltage presented on
the battery sense input, BAT, should represent a
single-cell potential for the battery under charge. A
resistor-dividerratioof

RB1
RB2

= N - 1

is recommended to maintain the battery voltage within
the valid range, where N is the number of cells, RB1 is
the resistor connected to the positive battery terminal,
and RB2 is the resistor connected to the negative bat­tery terminal. See Figure 1.

Note: This resistor-divider network input impedance to
end-to-end should be at least 200kΩ and less than 1 MΩ.

2

bq2002E/G

Fg2002E/G01.eps

bq2002E/G

BAT

V

SS

N
T
C

bq2002E/G

V

CC

V

CC

PACK +

T

S

V

SS

BAT pin connection Thermistor connection

TM

NTC = negative temperature coefficient thermistor.

RT

R3

R4

RB1

RB2

Mid-level

setting for TM

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

3

bq2002E/G

OSC

TM

CC

LED

V

CC

V

SS

BAT

INH

Clock

Phase

Generator

Timing

Control

Sample

History

A to D

Converter

MCV

Check

Power

Down

TS

Bd2002CEG.eps

Voltage

Reference

Power-On

Reset

TCO

Check

HTF

Check

LBAT

Check

Charge-Control

State Machine

PVD, - V

ALU

Figure 3. Block Diagram

Chip on

V

CC

4.0V

Battery Voltage

too High?

Battery

Temperature?

Charge
Pending

Fast

LED =

Low

S

D2

00

2C.e

p

s

Battery Voltage

too Low?

V

BAT

< 2V

V

TS

< 0.6

V

BAT

> 0.175

V

BAT

< 2V, and

V

TS

> V

CC

/2

V

BAT

>

2V

Top-off

LED = Z

Trickle

LED =

Flash

Trickle

LED = Z

V

BAT

> 2V

V

BAT

2V

V

CC

V

TS

> 0.6

V

CC

VCC,

0.175

V

CC

< V

BAT

V

CC

V

BAT

< 0.175

V

BAT

> 2V or
VTS < VCC/2 or
((PVD or - V or
Maximum Time Out)
and TM

Low)

V

BAT

V

TS

Maximum Time Out

2V or

VCC/2 or

(PVD or ­Maximum Time Out)
and TM = Low

V or

Figure 2. State Diagram

A ground-referenced negative temperature coefficient ther­mistor placed near the battery may be used as a low-cost
temperature-to-voltage transducer. The temperature
sense voltage input at TS is developed using a resistor­thermistor network between VCCand VSS. See Figure 1.

Starting ACharge Cycle

Either of two events starts a charge cycle (see Figure 4):

1.Applicationofpowerto V

CC

or

2. Voltage at the BAT pin falling through the maximum
cell voltage V

MCV

where

V

MCV

= 2V ±5%.

If the battery is within the configured temperature and
voltage limits, the IC begins fast charge. The valid bat­tery voltage range is V

LBAT<VBAT<VMCV

,where

4

bq2002E/G

Corre

-

sponding

Fast-Charge

Rate TM Termination

Typical Fast-

Charge and

Top-Off

Time Limits

(minutes)

Typical PVD

and -∆V

Hold-Off Time

(seconds)

Top-Off

Rate

Pulse­Trickle

Rate

Pulse-

Trickle

Width

(ms)

Maximum

Synchro

-

nized

Sampling

Period

(seconds)

bq2002E bq2002G

C/2 Mid PVD 200 160 300 Disabled C/32 73 18.7

1C Low PVD 80 80 150 C/16 C/32 37 18.7
2C High -∆V 40 40 75 Disabled C/32 18 9.4

Notes: Typical conditions= 25°C,VCC= 5.0V

Mid = 0.5*V

CC

±

0.5V

Tolerance on all timing is±12%.

Table 1. Fast-Charge Safety Time/Hold-Off/Top-Off Table

TD2002EG.eps

Fast ChargingVCC = 0 Fast Charging

CC Output

LED

Charge initiated by application of power

Charge initiated by battery replacement

Pulse-TrickleTop-Off

(optional)

73ms

1.17s 1.17s

See Table 1

Figure 4. Charge Cycle Phases