UNTRODE bq2002C Technical data

bq2002C

NiCd/NiMH Fast-Charge Management IC

Features

Fast charge of nickel cadmium

➤

or nickel-metal hydride batter
ies

Direct LED output displays

➤

chargestatus
Fast-charge termination by -∆V,

➤

maximum voltage, maximum
temperature, and maximum
time

Internal band-gap voltage ref

➤

erence

➤

Selectable pulse-trickle charge
rates

➤

Low-power mode

➤

8-pin 300-mil D I P or 150-mil
SOIC

Pin Connections

TM

LED

BAT
V

1

2

3

4

SS

8

7

6

5

CC

INH

V
TS

CC

General Description

The bq2002C Fast-Charge IC is a low­cost CMOS battery-charge controller

­providing reliable charge termination
for both NiCd and NiMH battery appli
cations. Controlling a current-limited
or constant-current supply allows the
bq2002C to be the basis for a cost­effective stand-alone or system-inte
grated charger. The bq2002C inte
grates fast charge with pulsed-trickle
control in a single IC for charging one
or more NiCd or NiMH batterycells.

­Fast charge is initiated on application

of t he charging supply or battery
replacement. 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 bq2002C pulse­trickles the battery per the pre­configured limits. Fast charge may be
inhibited using t h e INH pin. The
bq2002C may also be placed in low­standby-power mode t o reduce
system power consumption.

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

SLUS136 - SEPTEMBER 1997

1

bq2002C

Pin Descriptions

TM

LED

BAT

V

SS

TS

V

CC

INH

T ime rmodeinput

A three-level input that controls the settings
for the fast charge safety timer, voltage ter
mination mode, pulse-trickle, and voltage
hold-off time.

Charging output status

Open-drain output that indicates the charging
status.

Battery input voltage

Thebattery 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
Temperaturesense input

Input for an external battery temperature
monitoring thermistor.

Supply voltage input

5.0V±20%power input.

Charge inhibit input

When high, INH suspends t he fast charge in
progress. When returned low, the IC re­sumes operation at th e 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 pulse
trickle.

Functional Description

Figure 2 shows a state diagram a n d Figure 3 shows a
block diagram ofthe bq2002C.

Battery Voltageand Temperature
Measurements

­Battery voltage a n d 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-dividerratio 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 th e resistor connected to the n egative
battery terminal. SeeFigure 1.

Note:

This resistor-divider network input impedance to

end-to-end should be at least 200k
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

Ω

and less than 1MΩ.

and VSS. SeeFigure 1.

CC

-

V

CC

RB1

BAT

bq2002C

BAT pin connection Thermistor connection

RB2

V

SS

NTC = negative temperature coefficient thermistor.

R3

R4

Mid-level

setting for TM

V

CC

TM

bq2002C

T

V

SS

PACK +

RT

S

N
T
C

Fg2002/C.eps

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

2

bq2002C

OSC

V

CC

Chip on

4.0V

V

TS

V

BAT

0.84V < V

BAT

/2

> V

CC

Fast

LED =

Low

V

BAT

VTS < VCC/2 or
PVD or - V or
Maximum Time Out

Clock

Phase

Generator

Battery Voltage

too High?

< 2V

Battery Voltage

too Low?

Battery

Temperature?

> 2V or

V
V
V

BAT
BAT
TS

V

> V

2V

>

BAT

< 0.84V

V

BAT

< V

V

CC

TS

> 0.84V and
< 2V and

/2

CC

/2

Figure 2. State Diagram

Trickle
LED =

Flash

Trickle

LED = Z

Charge
Pending

V

BAT

V

> 2V

BAT

2V

2

SD

ps

.e

2C

00

TM

INH

Charge-Control

State Machine

Power-On

Reset

Timing

Control

Sample

History

PVD, - V

ALU

HTF

Check

CC

LED

Figure 3. Block Diagram

3

TCO

Check

TS

Power

Down

Voltage

Reference

A to D

Converter

LBAT

Check

MCV

Check

V

CC

V

SS

Bd2002CEG.eps

BAT

bq2002C

Fast ChargingVCC = 0 Fast Charging

CC Output

Charge initiated by application of power

Charge initiated by battery replacement

LED

Figure 4. Charge Cycle Phases

Starting A Charge Cycle

Either of twoevents starts a chargecycle (see Figure 4):

1.Application ofpower to V

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

MCV

where

V

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

V

LBAT

The valid temperature range isV

V

HTF

If V

≤

V

LBAT

or VTS≤

BAT

or

CC

= 2V±5%.

MCV

LBAT<VBAT<VMCV,

= 0.175∗VCC±

TS>VHTF

= 0.6∗VCC±

V

HTF

5%.

, the IC enters the charge-

where

20%

where

Pulse-Trickle

1s

See

Table 1

TD2002C1.eps

pending state. In this state pulse trickle charge is
applied to the battery and the LED flashes until the
voltage an d temperature come into t he allowed fast
charge range or V

≥

V

, the IC enters the Charge Complete/Battery

MCV

Absent state. In this state the LED is off and trickle

rises above V

BAT

. Anytime V

MCV

BAT

charge is applied to th e battery until the next new
charge cycle begins.

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

n

Peak voltage detection (PVD)

n

Negative delta voltage (-∆V)

n

Maximum voltage

n

Maximum temperature

n

Maximum time

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

Typical

Corresponding

Fast-Charge

Rate TM Termination

Fast-

Charge

Time Limits

(minutes)

Typical PVD

and -∆V
Hold-Off

Time (seconds)

Pulse-

Trickle

Rate

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

1C Low PVD 80 150 C/32 37 18.7
2C High -

Notes:

Typical conditions = 25°C, VCC= 5.0V
Mid = 0.5*V
Tolerance on all timing is ±12%.

V 40 75 C/32 18 9.4

∆

±0.5V

CC

4

Pulse-

Trickle

Pulse Width

(ms)

Maximum

Synchronized

Sampling

Period

(seconds)