Texas Instruments DV2002L2, BQ2002PN, BQ2002FSNTR, BQ2002FSN, BQ2002FPN Datasheet

bq2002/F

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 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 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 bq2002/F optionally 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.

Pin Connections

Pin Names

TM

Timer mode select input

TS

Temperature sense input

TM

1

8

CC

2

7

LED

Charging status output

VCC

Supply voltage input

LED

INH

BAT

3

6

VCC

BAT

Battery voltage input

INH

Charge inhibit input

CC

Charge control output

VSS

4

5

TS

VSS

System ground

8-Pin DIP or

Narrow SOIC

PN-200201.eps

bq2002/F Selection Guide

Part No.

TCO

HTF

LTF

-∆V

PVD

Fast Charge

tMTO

Top-Off

Maintenance

0.5 VCC

C/2

160

C/32

C/64

bq2002

None

None

1C

80

C/16

C/64

2C

40

None

C/32

0.5 VCC

C/2

160

C/32

C/64

bq2002F

None

None

1C

100

C/16

C/64

2C

55

None

C/32

SLUS131–JANUARY 1999 D

1

bq2002/F

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 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 VCC and VSS. See Figure 1.

				VCC		PACK +
					RT
		RB1	R3	VCC
	BAT			TM	TS
	bq2002/F			bq2002/F		N
		RB2	R4			T
						C
	VSS				VSS
	BAT pin connection		Mid-level			Thermistor connection
			setting for TM

NTC = negative temperature coefficient thermistor.

Fg2002/F01.eps

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

2

bq2002/F

	Chip on							Battery
V			4.0V					Voltage?
CC
				V	BAT			< 2V
	VTS > VCC/2
								Battery
							Temperature?

V	BAT	> 2V

VTS < VCC/2

Fast

LED = Low

V	BAT	> 2V

VTS < VCC/2 ((PVD or - V or

Maximum Time-Out) and TM = high)

V	2V
CC

Trickle

LED = Z

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

Top-off

LED = Z

Maximum Time-Out
or V	BAT	> 2V
or

VTS < VCC/2

SD2002/F01

Figure 2. State Diagram

	Clock
OSC	Phase
	Generator
TM	Timing		Sample	Voltage
	Control		History	Reference
INH
			∆	A to D
			PVD, - V	Converter
	Charge-Control		ALU
	State Machine
					MCV
					Check
					BAT
Power-On			TCO	Power
Reset			Check	Down
	CC	LED	TS	VCC	VSS
					Bd2002f.eps

Figure 3. Block Diagram

3

bq2002/F

VCC = 0

Fast Charging

Top-Off

Pulse-Trickle

Fast Charging

(optional)

286 s

CC Output

286 s

4576

s

See

Table 1

Charge initiated by application of power

Charge initiated by battery replacement

LED

TD2002F1.eps

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 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 VBAT < VMCV. The valid temperature range is VTS > VTCO where

VTCO = 0.5 VCC ±5%.

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)

Negative delta voltage (-∆V)

Maximum voltage

Maximum temperature

Maximum time

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

				Typical Fast-Charge
				and Top-Off					Pulse-
				Time Limits
Corresponding				(minutes)		Typical PVD		Pulse-	Trickle
Fast-Charge						and -∆V Hold-Off	Top-Off	Trickle	Period
				bq2002	bq2002F
Rate		TM	Termination			Time (seconds)	Rate	Rate	(ms)
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 * VCC ±5V
	Tolerance on all timing is ±20%.

4