TEXAS INSTRUMENTS bq2002C Technical data

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bq2002C

NiCd/NiMH Fast-Charge Management IC

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
Selectable pulse-trickle charge

➤

rates

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

SOIC

Pin Connections

TM

LED

BAT
V

SS

1

2

3

4

8

CC

7

INH

V

6

CC

TS

5

General Description

The bq2002C F ast-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 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.

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 the INH pin. The
bq2002C may also be placed in low­standby-power mode to reduce
system power consumption.

TS Temperature sense input
V

CC

Supply voltage input
INH Charge inhibit input
CC Charge control output

9/97 B

8-Pin DIP or

Narrow SOIC

PN-200201.eps

1

bq2002C

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, 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
Temperaturesenseinput

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 pulse
trickle.

Functional Description

Figure 2 shows a state diagram and Figure 3 shows a
block diagram of the bq2002C.

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

= 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

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

20

D

S

s

p

.e

C

02

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 ACharge Cycle

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

1.Applicationofpowerto 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

V

LBAT

The valid temperature range is V

V

HTF

If V

BAT

≤ V

LBAT

or VTS≤ V

or

CC

= 2V ±5%.

MCV

LBAT<VBAT<VMCV,

= 0.175 ∗ VCC±20%

TS>VHTF

= 0.6 ∗ VCC±5%.

, the IC enters the charge-

HTF

where

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 and temperature come into the allowed fast
charge range or V
≥ V

, the IC enters the Charge Complete/Battery

MCV

rises above V

BAT

. Anytime V

MCV

BAT

Absent state. In this state the LED is off and trickle
charge is applied to the 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 -∆V 40 75 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%.

4

Pulse-

Trickle

Pulse Width

(ms)

Maximum

Synchronized

Sampling

Period

(seconds)

bq2002C

PVD and -∆VTermination

There are two modes for voltage termination, depend
ing on the state of TM. For -∆V (TM = high), if V
lower than any previously measured value by 12mV
±3mV, fast charge is terminated. For PVD (TM = low or
mid), a decrease of 2.5mV ±2.5mV terminates fast
charge. The PVD and -∆V tests are valid in the range
1V<V

BAT

<2V.

BAT

Synchronized Voltage Sampling

Voltagesampling at the BAT pin for PVD and -∆V termi
nation may be synchronized to an external stimulus
using the INH input. Low-high-low input pulses
between 100ns and 3.5ms in width must be applied at
the INH pin with a frequency greater than the “maxi
mum synchronized sampling period” set by the state of
the TM pin as shown in Table 1. Voltage is sampled on
the falling edge of such pulses. If the time between
pulses is greater than the synchronizing period, voltage
sampling “free-runs” at once every 17 seconds. A sample
is taken by averaging together voltage measurements
taken 57µs apart. The IC takes 32 measurements in
PVD mode and 16 measurements in -∆V mode. The
resulting sample periods (9.17 and 18.18ms, respec­tively) filter out harmonics centered around 55 and
109Hz. This technique minimizes the effect of any AC
line ripple that may feed through the power supply from
either 50 or 60Hz AC sources. If the INH input remains
high for more than 12ms, the voltage sample history
kept by the IC and used for PVD and -∆V termination
decisions is erased and a new history is started. Such a
reset is required when transitioning from free-running
to synchronized voltage sampling. The response of the
IC to pulses less than 100ns in width or between 3.5ms
and 12ms is indeterminate. The tolerance on all timing
is±12%.

Voltage Termination Hold-off

A hold-off period occurs at the start of fast charging.
During the hold-off time, the PVD and -∆V terminations
are disabled. This avoids premature termination on the
voltage spikes sometimes produced by older batteries
when fast-charge current is first applied. Maximum
voltage and temperature terminations are not affected
by the hold-off period.

Maximum Voltage, Temperature,and Time

Any time the voltage on the BAT pin exceeds the maxi
mum cell voltage, V

Maximum temperature termination occurs anytime the
voltage on the TS pin falls below the temperature cut-off
threshold V

TCO,

,fast charge is terminated.

MCV

where

= 0.5 ∗VCC±5%.

V

TCO

Maximum charge time is configured using the TM pin.
Time settings are available for corresponding charge

-

rates of C/2, 1C, and 2C. Maximum time-out termina
tion is enforced on the fast-charge phase,then reset, and

is

enforced again on the top-off phase, if selected. There is
no time limit on the trickle-charge phase.

Pulse-Trickle Charge

Pulse-trickle is used to compensate for self-discharge
while the battery is idle in the charger. The battery is
pulse-trickle charged by driving the CC pin active once
per second for the period specified in Table 1. This

­results in a trickle rate of C/32.

TM Pin

­The TM pin is a three-level pin used to select the

charge timer, top-off,voltage termination mode,trickle
rate, and voltage hold-off period options. Table 1
describes the states selected by the TM pin. The
mid-level selection input is developed by a resistor
divider between V
age on TM at V

CC

and ground that fixes the volt

CC

/2 ± 0.5V. See Figure 4.

Charge Status Indication

A fast charge in progress is uniquely indicated when the
LED

pin goes low. In the charge pending state, the LED
pin is driven low for 500ms, then to high-Z for 500ms.
The LED
conditions. Figure 2 outlines the state of the LED
during charge.

pin is driven to the high-Z state for all other

Charge Inhibit

Fast charge and top-off may be inhibited by using the
INH pin. When high, INH suspends all fast charge and
top-off activity and the internal charge timer. INH
freezes the current state of LED
removed. Temperature monitoring is not affected by the
INH pin. During charge inhibit, the bq2002C continues
to pulse-trickle charge the battery per the TM selection.
When INH returns low, charge control and the charge
timer resume from the point where INH became active.

until inhibit is

Low-Power Mode

The IC enters a low-power state when V
above the power-downthreshold(V

= VCC- (1V ±0.5V)

V

­Both the CC pin and the LED

high-Z state. The operating current is reduced to less
than 1µA in this mode. When V
below V
new charge cycle begins.

PD

PD

, the IC pulse-trickle charges until the next

PD

pin are driven to the

BAT

BAT

) where

returns to a value

-

-

pin

is driven

5

bq2002C

Absolute Maximum Ratings

Symbol Parameter Minimum Maximum Unit Notes

V

CC

V

T

T

OPR

T

STG

T

SOLDER

T

BIAS

VCCrelative to V

SS

DC voltage applied on any pin
excluding V

relative to V

CC

SS

Operating ambient temperature 0 +70 °C Commercial
Storage temperature -40 +85 °C
Soldering temperature - +260 °C 10 sec max.
Temperature under bias -40 +85 °C

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional opera

tion should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Expo
sure to conditions beyond the operational limits for extended periods of time may affect device reliability.

-0.3 +7.0 V

-0.3 +7.0 V

-

-

DC Thresholds (T

= 0 to 70°C; V

A

CC

20%)

±

Symbol Parameter Rating Tolerance Unit Notes

V

TCO

Temperature cutoff 0.5*V

CC

±5%

V

VTS≤ V

inhibits/terminates

TCO

fast charge

V

HTF

High-temperature fault

0.6 ∗ V

CC

±5%

V

VTS≤ V

inhibits fast charge

HTF

start

V

MCV

Maximum cell voltage 2

±5%

V

V

≥ V

BAT

inhibits/terminates

MCV

fast charge

V

-∆V

LBAT

Minimum cell voltage
BAT input change for

0.175 ∗ V

-12

CC

±20%

±3

V

mV

V

BAT

≤ V

inhibits fast charge

LBAT

-∆V detection

PVD BAT input change for

-2.5

±2.5

mV

PVD detection

6

bq2002C

Recommended DC Operating Conditions (T

= 0 to 70°C)

A

Symbol Condition Minimum Typical Maximum Unit Notes

V

CC

V

DET

V

BAT

V

TS

V

IH

V

IM

V

IL

Supply voltage 4.0 5.0 6.0 V

-∆V, PVD detect voltage 1 - 2 V
Battery input 0 - V
Thermistor input 0.5 - V

CC

CC

V

VVTS< 0.5V prohibited
Logic input high 0.5 - - V INH
Logic input high V
Logic input mid

- 0.5 - - V TM

CC

V

CC

- 0.5

2

-

V

CC

05+ .

2

VTM

Logic input low - - 0.1 V INH
Logic input low - - 0.5 V TM

V

OL

V

PD

Logic output low - - 0.8 V LED, CC, IOL= 10mA
Power down VCC- 1.5 - VCC- 0.5 V V

BAT

V

≥

PD

max. powers
down bq2002C;
V

< VPDmin. =

BAT

normal operation.

I

CC

I

SB

I

OL

I

L

I

OZ

Supply current - - 500

Standby current - - 1

LED, CC sink 10 - - mA @VOL= VSS+ 0.8V
Input leakage - ­Output leakage in

high-Z state

Note: All voltages relative to VSS.

-5 - -

7

A Outputs unloaded,

µ

V

= 5.1V

CC

AVCC= 5.1V, V

µ

1

±

A INH, CC, V = VSSto V

µ

A LED,CC

µ

BAT

= V

PD

CC

bq2002C

Impedance

Symbol Parameter Minimum Typical Maximum Unit

R

BAT

R

TS

Battery input impedance 50 - - M
TS input impedance 50 - - M

Ω
Ω

Timing (T

Symbol Parameter Minimum Typical Maximum Unit Notes

d

FCV

Note: Typical is at TA= 25°C,VCC= 5.0V.

= 0 to +70°C; V

A

Time base variation -12 - 12 %

CC

10%)

±

8

bq2002C

8-Pin DIP(PN

E1

E

C

e

)

8-Pin PN(0.300" DIP

D

Dimension

A 0.160 0.180 4.06 4.57

A1 0.015 0.040 0.38 1.02

B 0.015 0.022 0.38 0.56

B1 0.055 0.065 1.40 1.65

A

A1

L

B1

C 0.008 0.013 0.20 0.33
D 0.350 0.380 8.89 9.65
E 0.300 0.325 7.62 8.26

E1 0.230 0.280 5.84 7.11

e 0.300 0.370 7.62 9.40

S

B

G

G 0.090 0.110 2.29 2.79
L 0.115 0.150 2.92 3.81

S 0.020 0.040 0.51 1.02

Min. Max. Min. Max.

)

Inches Millimeters

9

bq2002C

8-Pin SOIC Narrow (SN)

8-Pin SN(0.150" SOIC

Inches Millimeters

Dimension

A 0.060 0.070 1.52 1.78

A1 0.004 0.010 0.10 0.25

B 0.013 0.020 0.33 0.51
C 0.007 0.010 0.18 0.25
D 0.185 0.200 4.70 5.08
E 0.150 0.160 3.81 4.06

e 0.045 0.055 1.14 1.40
H 0.225 0.245 5.72 6.22
L 0.015 0.035 0.38 0.89

Min. Max. Min. Max.

)

10

Data Sheet Revision History

Change No. Page No. Description

1 All Revised format and outline of this data sheet

Note: Change 1 = Sept. 1997 B changes from Dec. 1995.

Ordering Information

bq2002C

PackageOption:

PN = 8-pin plastic DIP
SN = 8-pin narrow SOIC

bq2002C

Device:

bq2002C Fast-ChargeIC

11

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