Texas Instruments DV2002TL2, BQ2002TSNTR, BQ2002TSN, BQ2002TPN, BQ2002DSNTR Datasheet

bq2002D/T

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 rate of rise of temperature, maximum voltage, maximum temperature, and maximum time

Internal band-gap voltage reference

Optional top-off charge (bq2002T only)

Selectable pulse-trickle charge rates (bq2002T only)

Low-power mode

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

General Description

The bq2002D/T Fast-Charge IC are low-cost CMOS battery-charge controllers able to provide reliable charge termination for both NiCd and NiMH battery applications. Controlling a current-limited or constant-current supply allows the bq2002D/T to be the basis for a cost-effective stand-alone or system-integrated charger. The bq2002D/T 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:

Rate of temperature rise

Maximum voltage

Maximum temperature

Maximum time

After fast charge, the bq2002T optionally tops-off and pulse-trickles the battery per the pre-configured limits. Fast charge may be inhibited using the INH pin. The bq2002D/T may be placed in low-standby-power mode to reduce system power consumption.

Pin Connections

Pin Names

TM

Timer mode select input

TS

Temperature sense input

TM

1

8

CC

VCC

Supply voltage input

2

7

LED

Charging status output

LED

INH

BAT

3

6

VCC

BAT

Battery voltage input

INH

Charge inhibit input

VSS

4

5

TS

VSS

System ground

CC

Charge control output

8-Pin DIP or

Narrow SOIC

PN-200201.eps

bq2002D/T Selection Guide

Part No.

TCO

HTF

LTF

Fast Charge

Time-Out

Top-Off

Maintenance

0.225 VCC

0.25 VCC

0.4 VCC

C/4

320 min

C/64

C/256

bq2002D

1C

80 min

C/16

C/256

2C

40 min

None

C/128

0.225 VCC

0.25 VCC

C/4

440 min

None

None

bq2002T

None

1C

110 min

None

None

2C

55 min

None

None

SLUS133–JANUARY 2000 E

1

bq2002D/T

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

Figures 2 and 3 show state diagrams of bq2002D/T and Figure 4 shows the block diagram of the bq2002D/T

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.

			VCC		PACK +
				RT1
	RB1	R3	VCC
BAT			TM	TS
bq2002D/T			bq2002D/T RT2		N
	RB2	R4			T
					C
VSS				VSS
BAT pin connection		Mid-level		Thermistor connection
		setting for TM

NTC = negative temperature coefficient thermistor.

F2002DT1.eps

Figure 1. Voltage and Temperature Monitoring and TM Pin Configuration

2

											bq2002D/T
	Chip on			Battery Voltage
V	CC	4.0V			too High?	V
						BAT > 2V
		V	BAT		< 2V
VTS > 0.25V VCC					Battery
					Temperature?	VTS < 0.25V		VCC
										Charge
										Pending
		Fast Charge,								Off,
									CC = Low
		CC = Z
									LED = Low
		LED = Low			V	BAT	< 2V and
					VTS > 0.25V VCC					VBAT > 2V
		T/		t or
		VBAT > 2V or								VBAT	2V
		VTS < 0.25V VCC or
		Maximum Time Out								Off,
									CC = Low
									LED = Z

SD2002D.eps

Figure 2. bq2002D State Diagram

Chip on

Battery Voltage

V

CC

4.0V

too High?

V

BAT > 2V

V

BAT

< 2V

0.25 VCC < VTS < 0.6

VCC

Battery

Temperature?

VTS > 0.6

VCC or

VTS < 0.25

VCC

Charge

( T/ t or

Pending

Maximum Time Out)

Fast

Trickle

and TM = High

LED =

LED =

Low

Low

VBAT < 2V and

VBAT > 2V or

VTS < 0.6

VCC and

VBAT > 2V

Top-off

VCC or

VTS > 0.25

VCC

LED = Z

VTS < 0.225

(( T/

t or

Maximum Time Out)

VBAT

2V

and TM = High)

Trickle

VBAT > 2V or

LED = Z

VTS < 0.225 VCC or

Maximum Time Out

SD2002T.eps

Figure 3. bq2002T State Diagram

3

bq2002D/T

	Clock
OSC	Phase
	Generator
TM	Timing		Sample	Voltage
	Control		History	Reference
INH
			T/ t	A to D
	Charge-Control		ALU	Converter
	State Machine
					HTF/
					LTF
					Check
Power-On			MCV	Power	TCO	TS
			Check	Down
Reset					Check
	CC	LED	BAT	VCC	VSS
						Bd2002TD.eps

Figure 4. Block Diagram

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 in proximity to 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-thermistor network between VCC and VSS. See Figure 1.

Starting A Charge Cycle

Either of two events starts a charge cycle (see Figure 5):

1.Application of power to VCC or

2.Voltage at the BAT pin falling through the maximum cell voltage 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 VHTF < VTS < VLTF for the bq2002T and VHTF < VTS for the bq2002D where:

VLTF = 0.4 VCC ±5%.

VHTF = 0.25 VCC ±5% (bq2002T only).

If the battery voltage or temperature is outside of these limits, the IC pulse-trickle charges until the temperature falls within the allowed fast charge range or a new charge cycle is started.

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

Rate of temperature rise

Maximum voltage

Maximum temperature

Maximum time

∆T/∆t Termination

The bq2002D/T samples at the voltage at the TS pin every 19s and compares it to the value measured three samples earlier. If the voltage has fallen 25.6mV or more, fast charge is terminated. The ∆T/∆t termination test is valid only when VTCO < VTS < VLTF for the bq2002T and VTCO < VTS for the bq2002D.

Temperature Sampling

A sample is taken by averaging together 16 measurements taken 57µs apart. The resulting sample period (18.18ms) filters out harmonics around 55Hz. This tech-

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