Texas Instruments BQ2002GSN, BQ2002GPN, BQ2002ESNTR, BQ2002ESN-SITR, BQ2002ESN-SI Datasheet

bq2002E/G

NiCd/NiMH Fast-Charge Management ICs

Features

Fast charge of nickel cadmium or nickel-metal hydride batteries

Direct LED output displays charge status

Fast-charge termination by - V, maximum voltage, maximum temperature, and maximum time

Internal band-gap voltage reference

Optional top-off charge

Selectable pulse trickle charge rates

Low-power mode

8-pin 300-mil DIP or 150-mil SOIC

General Description

The bq2002E and bq2002G FastCharge ICs are low-cost CMOS bat- tery-charge controllers providing reliable charge termination for both NiCd and NiMH battery applications. Controlling a current-limited or con- stant-current supply allows the bq2002E/G to be the basis for a costeffective stand-alone or system-inte- grated charger. The bq2002E/G integrates fast charge with optional top-off and pulsedtrickle 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.

Fast charge is terminated by any of the following:

Peak voltage detection (PVD)

Negative delta voltage (- V)

Maximum voltage

Maximum temperature

Maximum time

After fast charge, the bq2002E/G optionally tops-off and pulse-trickles the battery per the pre-configured limits. Fast charge may be inhibited using the INH pin. The bq2002E/G may also be placed in low-standby-power mode to reduce system power consumption.

The bq2002E differs from the bq2002G 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.

Pin Connections

Pin Names

TM

Timer mode select input

TS

Temperature sense input

TM

1

8

CC

Charging status output

VCC

Supply voltage input

LED

LED

2

7

INH

BAT

Battery voltage input

INH

Charge inhibit input

BAT

3

6

VCC

VSS

System ground

CC

Charge control output

VSS

4

5

TS

8-Pin DIP or

Narrow SOIC

PN-200201.eps

bq2002E/G Selection Guide

Part No.

LBAT

TCO

HTF

LTF

- V

PVD

Fast Charge

tMTO

Top-Off

Maintenance

bq2002E

0.175

0.5

0.6

None

C/2

200

None

C/32

VCC

VCC

VCC

1C

80

C/16

C/32

2C

40

None

C/32

bq2002G

0.175

0.5

0.6

None

C/2

160

None

C/32

VCC

VCC

VCC

1C

80

C/16

C/32

2C

40

None

C/32

2/99

1

bq2002E/G

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.
VSS	System ground
TS	Temperature sense input
	Input for an external battery temperature
	monitoring thermistor.
VCC	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.

CCCharge control output

An open-drain output used to control the charging current to the battery. CC switching 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 bq2002E/G.

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 .

				VCC		PACK +
					RT
		RB1	R3	VCC
	BAT			TM	TS
	bq2002E/G			bq2002E/G		N
		RB2	R4			T
						C
	VSS				VSS
	BAT pin connection		Mid-level			Thermistor connection
			setting for TM

NTC = negative temperature coefficient thermistor.

Fg2002E/G01.eps

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

2

bq2002E/G

Chip on

Battery Voltage

V

CC

4.0V

too High?

V

>

2V

BAT

V

BAT

< 2V

Battery Voltage

too Low?

VBAT < 0.175

VCC

0.175

VCC < VBAT

VTS > 0.6

VCC

Battery

VTS < 0.6

VCC

Temperature?

Charge

(PVD or -

V or

Pending

Maximum Time Out)

Fast

Trickle

and TM = Low

LED =

LED =

Low

VBAT > 0.175

VCC,

Flash

V

BAT

< 2V, and

VBAT > 2V

Top-off

VBAT > 2V or

V

TS

> V

CC

/2

LED = Z

VTS < VCC/2 or

((PVD or - V or

Maximum Time Out)

VBAT

2V

and TM

Low)

Trickle

VBAT

2V or

LED = Z

VTS VCC/2 or Maximum Time Out

SD2002C.eps

	Figure 2. State Diagram
	Clock
OSC	Phase
	Generator
TM	Timing		Sample		Voltage
	Control		History		Reference
INH
			PVD, - V			A to D
	Charge-Control			ALU	Converter
	State Machine
						LBAT
						Check
						MCV	BAT
Power-On			HTF	TCO	Power	Check
Reset			Check Check		Down
	CC	LED		TS	VCC		VSS
							Bd2002CEG.eps

Figure 3. Block Diagram

3

bq2002E/G
VCC = 0	Fast Charging	Top-Off	Pulse-Trickle	Fast Charging
		(optional)
CC Output		73ms	See Table 1
		1.17s	1.17s
	Charge initiated by application of power
		Charge initiated by battery replacement
LED
				TD2002EG.eps

Figure 4. Charge Cycle Phases

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 resistorthermistor network between VCC and VSS. See Figure 1.

Starting A Charge Cycle

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

1.Application of power to VCC or

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

VMCV = 2V ± 5%.

If the battery is within the configured temperature and voltage limits, the IC begins fast charge. The valid battery voltage range is VLBAT < VBAT < VMCV, where

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

				Typical Fast-						Maximum
				Charge and
				Top-Off						Synchro-
Corre-				Time Limits		Typical PVD			Pulse-	nized
sponding				(minutes)		and - V		Pulse-	Trickle	Sampling
Fast-Charge						Hold-Off Time	Top-Off	Trickle	Width	Period
				bq2002E	bq2002G
Rate		TM	Termination			(seconds)	Rate	Rate	(ms)	(seconds)
C/2		Mid	PVD	200	160	300	Disabled	C/32	73	18.7
1C		Low	PVD	80	80	150	C/16	C/32	37	18.7
2C		High	- V	40	40	75	Disabled	C/32	18	9.4
Notes:	Typical conditions = 25°C, VCC = 5.0V
	Mid = 0.5 * VCC ± 0.5V
	Tolerance on all timing is ± 12%.

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