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.

System ground

TS

Temperature sense input

Input for an external battery temperature

monitoring thermistor.

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

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

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 bat-

tery terminal. See Figure 1.

Note: This resistor-divider network input impedance to

end-to-end should be at least 200k

Ω and less than 1 MΩ.

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 resistor-

2

bq2002/F

Fg2002/F01.eps

bq2002/F

BAT

VSS

N

T

C

bq2002/F

VCC

VCC

PACK +

TS

VSS

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