TEXAS INSTRUMENTS bq2002, bq2002F Technical data

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bq2002/F

NiCd/NiMH Fast-Charge Management ICs

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

Pin Connections

TM

LED

BAT

V

1

2

3

4

SS

8

CC

7

INH

V

6

CC

TS

5

General Description

The bq2002 and bq2002/F Fast-Charge
ICs are low-cost CMOS battery-charge

­controllers providing reliable charge
termination for both NiCd and NiMH
battery applications. Controlling a
current-limited or constant-current
supply allows the bq2002/F to be the
basis for a cost-effective stand-alone or
system-integrated charger. The
bq2002/F 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.

Pin Names

TM Timer mode select input

LED

BAT Battery voltage input

V

SS

Charging status output

System ground

Fast charge is terminated by any of
the following:

Peak voltage detection (PVD)

n

Negative delta voltage (-∆V)

n

Maximum voltage

n

Maximum temperature

n

Maximum time

n

After fast charge, the bq2002/F op

-

tionally tops-off and pulse-trickles the
battery per the pre-configured limits.
Fast charge may be inhibited using
the INH pin. The bq2002/F may also
be placed in low-standby-power mode

­to reduce system power consumption.

The bq2002F differs from the
bq2002 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 Table 1.

TS Temperature sense input

V

CC

Supply voltage input

INH Charge inhibit input

CC Charge control output

-

8-Pin DIP or

Narrow SOIC

PN-200201.eps

bq2002/F Selection Guide

Part No. TCO HTF LTF

bq2002

bq2002F

SLUS131–JANUARY 1999 D

0.5 ∗ V

0.5 ∗ V

None None

CC

None None

CC

PVD Fast Charge t

-∆V

MTO

Top-Off Maintenance

✔ C/2 160 C/32 C/64
✔ 1C 80 C/16 C/64

✔ 2C 40 None C/32

✔ C/2 160 C/32 C/64
✔ 1C 100 C/16 C/64

✔ 2C 55 None C/32

1

bq2002/F

Pin Descriptions

TM

LED

BAT

V

SS

TS

V

CC

INH

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.

Charging output status

Open-drain output that indicates the charging
status.

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.

System ground

Temperature sense input

Input for an external battery temperature
monitoring thermistor.

Supply voltage input

5.0V±20% power input.

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

Figure 2 shows a state diagram and Figure 3 shows a
block diagram of the bq2002/F.

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

= N - 1

RB2

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.

-

A ground-referenced negative temperature coefficient
thermistor placed near the battery may be used as a low­cost temperature-to-voltage transducer. The temperature
sense voltage input at TS is developed using a resistor­thermistor network between V

and VSS. See Figure 1.

CC

-

V

CC

RB1

BAT

bq2002/F

BAT pin connection Thermistor connection

RB2

V

SS

NTC = negative temperature coefficient thermistor.

R3

R4

Mid-level

setting for TM

V

CC

TM

bq2002/F

T

V

SS

PACK +

RT

S

N
T
C

Fg2002/F01.eps

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

2

bq2002/F

OSC

Chip on

4.0V

V

CC

VTS > VCC/2 VTS < VCC/2

V

BAT

VTS < VCC/2

((PVD or - V or
Maximum Time-Out)

Fast

LED = Low

(PVD or - V or
Maximum Time-Out)
and TM = high

and TM = high)

< 2V

V

BAT

Temperature?

> 2V

Battery
Voltage?

Battery

Top-off

LED = Z

V

V

CC

Maximum Time-Out

Figure 2. State Diagram

Clock

Phase

Generator

> 2V

BAT

2V

or

or

VTS < VCC/2

Trickle

LED = Z

V

BAT

SD2002/F01

> 2V

TM

INH

Charge-Control

State Machine

Power-On

Reset

Timing

Control

PVD, -∆V

CC

LED

Figure 3. Block Diagram

3

Sample

History

ALU

TCO

Check

TS

Voltage

Reference

A to D

Converter

Check

Power

Down

V

CC

MCV

V

BAT

SS

Bd2002f.eps

bq2002/F

Fast ChargingVCC = 0 Fast Charging

CC Output

Charge initiated by application of power

LED

(optional)

286

4576

Figure 4. Charge Cycle Phases

Starting A Charge Cycle

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

1. Application of power to V

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

MCV

where

V

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

TS>VTCO

V

TCO

or

CC

= 2V ±5%.

MCV

BAT<VMCV

. The valid tempera-

where

= 0.5 ∗ VCC±5%.

Pulse-TrickleTop-Off

See

Table 1

286

s

TD2002F1.eps

s

s

Charge initiated by battery replacement

If the battery voltage or temperature is outside of these
limits, the IC pulse-trickle charges until the next new
charge cycle begins.

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

Peak voltage detection (PVD)

n

n

Negative delta voltage (-∆V)

n

Maximum voltage

n

Maximum temperature

n

Maximum time

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

Typical Fast-Charge

and Top-Off
Time Limits

Corresponding

Fast-Charge

Rate TM Termination

(minutes) Typical PVD

and -∆V Hold-Off

bq2002 bq2002F

Time (seconds)

Top-Off

Rate

C/2 Mid PVD 160 160 600 C/32 C/64 9.15

1C Low PVD 80 100 300 C/16 C/64 18.3

2C High -∆V 40 40 150 Disabled C/32 18.3

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

Mid = 0.5*V

CC

5V

±

Tolerance on all timing is±20%.

4

Pulse-

Trickle

Rate

Pulse­Trickle
Period

(ms)