Texas Instruments DV2002TL2, BQ2002TSNTR, BQ2002TSN, BQ2002TPN, BQ2002DSNTR Datasheet

Features

➤

Fast charge of nickel cadmium
or nickel-metal hydride batter

-

ies

➤

Direct LED output displays
charge status

➤

Fast-charge termination by
rate of rise of temperature,
maximum voltage, maximum
temperature, and maximum
time

➤

Internal band-gap voltage ref

-

erence

➤

Optional top-off charge (bq2002T
only)

➤ Selectable pulse-trickle charge

rates (bq2002T only)

➤ Low-power mode

➤ 8-pin 300-mil DIP or 150-mil

SOIC

General Description

The bq2002D/T Fast-Charge IC are
low-cost CMOS battery-charge control

-

lers able to provide reliable charge ter

-

mination for both NiCd and NiMH bat

­tery applications. Controlling a
current-limited or constant-current
supply allows the bq2002D/T to be the
basis for a cost-effective stand-alone or
system-integrated charger. The
bq2002D/T integrates fast charge with
optional top-off and pulsed-trickle con

­trol 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 re

­placement. 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

Rate of temperature rise

n

Maximum voltage

n

Maximum temperature

n

Maximum time

After fast charge, the bq2002T option

­ally tops-off and pulse-trickles the
battery per the pre-configured limits.
Fast charge may be inhibited using
the INH pin. The bq2002D/T may be
placed in low-standby-power mode to
reduce system power consumption.

1

NiCd/NiMH Fast-Charge Management ICs

bq2002D/T

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

bq2002D/T Selection Guide

Part No. TCO HTF LTF Fast Charge Time-Out Top-Off Maintenance

bq2002D

0.225 ∗ V

CC

0.25 ∗ V

CC

0.4 ∗ V

CC

C/4 320 min C/64 C/256

1C 80 min C/16 C/256
2C 40 min None C/128

bq2002T

0.225 ∗ V

CC

0.25 ∗ V

CC

None

C/4 440 min None None

1C 110 min None None
2C 55 min None None

SLUS133–JANUARY 2000 E

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

Temperature sense input

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, and pulse trickle.

Functional Description

Figures 2 and 3 show state diagrams of bq2002D/T and
Figure 4 shows the block diagram of the bq2002D/T

Battery Voltage and 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-divider ratio of:

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.

2

bq2002D/T

F2002DT1.eps

bq2002D/T

BAT

V

SS

N
T
C

bq2002D/T

V

CC

V

CC

PACK +

T

S

V

SS

BAT pin connection Thermistor connection

TM

NTC = negative temperature coefficient thermistor.

RT1

RT2

R3

R4

RB1

RB2

Mid-level

setting for TM

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

3

bq2002D/T

Chip on

V

CC

4.0V

Battery Voltage

too High?

Battery

Temperature?

Charge
Pending

Fast Charge,

CC = Z

LED = Low

SD2002D.eps

V

BAT

< 2V

V

BAT

< 2V and

V

BAT

>

2V

Off,

CC = Low

LED = Low

Off,

CC = Low

LED = Z

V

BAT

> 2V

V

BAT

2V

V

TS

> 0.25V

V

CC

V

TS

> 0.25V

V

CC

V

TS

< 0.25V

V

CC

V

BAT

> 2V or

V

TS

< 0.25V

V

CC

or

Maximum Time Out

T/ t or

Figure 2. bq2002D State Diagram

Chip on

V

CC

4.0V

Battery Voltage

too High?

( T/

t or
Maximum Time Out)
and TM = High

Battery

Temperature?

Charge
Pending

Fast

LED =

Low

Top-off

LED = Z

SD2002T.eps

V

BAT

< 2V

V

BAT

>

2V

0.25 VCC < VTS < 0.6 V

CC

Trickle
LED =

Low

Trickle

LED = Z

V

BAT

> 2V or
VTS < 0.225 VCC or
Maximum Time Out

V

BAT

> 2V or
VTS < 0.225 VCC or
(( T/ t or
Maximum Time Out)
and TM = High)

V

BAT

< 2V and
VTS < 0.6 VCC and
VTS > 0.25 V

CC

V

BAT

> 2V

V

BAT

2V

VTS > 0.6 VCC or
VTS < 0.25 V

CC

Figure 3. bq2002T State Diagram

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

A ground-referenced negative temperature coefficient ther

­mistor placed in proximity to the battery may be used as a
low-cost temperature-to-voltage transducer. The tempera

­ture sense voltage input at TS is developed using a
resistor-thermistor network between V

CC

and VSS. See

Figure 1.

Starting A Charge Cycle

Either of two events starts a charge cycle (see Figure 5):

1. Application of power to V

CC

or

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

V

MCV

= 2V ±5%.

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

­tery voltage range is V

BAT<VMCV

. The valid tempera

­ture range is V

HTF<VTS<VLTF

for the bq2002T and

V

HTF<VTS

for the bq2002D where:

V

LTF

= 0.4 ∗ VCC±5%.

V

HTF

= 0.25 ∗ VCC±5% (bq2002T only).

If the battery voltage or temperature is outside of these
limits, the IC pulse-trickle charges until the tempera­ture falls within the allowed fast charge range or a new
charge cycle is started.

Fast charge continues until termination by one or more of
the four possible termination conditions:

n

Rate of temperature rise

n

Maximum voltage

n

Maximum temperature

n

Maximum time

∆T/∆t Termination

The bq2002D/T samples at the voltage at the TS pin ev

­ery 19s and compares it to the value measured three
samples earlier. If the voltage has fallen 25.6mV or
more, fast charge is terminated. The ∆T/∆t termination
test is valid only when V

TCO<VTS<VLTF

for the

bq2002T and V

TCO<VTS

for the bq2002D.

Temperature Sampling

A sample is taken by averaging together 16 measure

­ments taken 57µs apart. The resulting sample period
(18.18ms) filters out harmonics around 55Hz. This tech

-

4

bq2002D/T

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

Bd2002TD.eps

Voltage

Reference

Power-On

Reset

TCO

Check

HTF/

LTF

Check

Charge-Control

State Machine

T/ t

ALU

Figure 4. Block Diagram