UNITRODE bq2004E, bq2004H Technical data

bq2004E/H

Features

Fast charge and conditioning of nickel cadmium or nickel-metal hydride batteries

Hysteretic PWM switch-mode current regulation or gated control of an external regulator

Easily integrated into systems or used as a stand-alone charger

Pre-charge qualification of temperature and voltage

Configurable, direct LED outputs display battery and charge status

Fast-charge termination by temperature/ time, peak volume detection, - V, maximum voltage, maximum temperature, and maximum time

Optional top-off charge and pulsed current maintenance charging

Logic-level controlled low-power mode (< 5µA standby current)

bq2004E/H

Fast-Charge ICs

General Description

The bq2004E and bq2004H Fast Charge ICs provide comprehensive fast charge control functions together with high-speed switching power control circuitry on a monolithic CMOS device.

Integration of closed-loop current control circuitry allows the bq2004 to be the basis of a cost-effective solution for stand-alone and systemintegrated chargers for batteries of one or more cells.

Switch-activated discharge-before- charge allows bq2004E/H-based chargers to support battery conditioning and capacity determination.

High-efficiency power conversion is accomplished using the bq2004E/H as a hysteretic PWM controller for switch-mode regulation of the charging current. The bq2004E/H may alternatively be used to gate an externally regulated charging current.

Fast charge may begin on application of the charging supply, replacement of the battery, or switch depression. For safety, fast charge is inhibited unless/until the battery tempera-

ture and voltage are within configured limits.

Temperature, voltage, and time are monitored throughout fast charge. Fast charge is terminated by any of the following:

Rate of temperature rise ( T/ t)

Peak voltage detection (PVD)

Negative delta voltage (- V)

Maximum voltage

Maximum temperature

Maximum time

After fast charge, optional top-off and pulsed current maintenance phases with appropriate display mode selections are available.

The bq2004H differs from the bq2004E only in that fast charge, hold-off, and top-off time units have been scaled up by a factor of two, and the bq2004H provides different display selections. Timing differences between the two ICs are illustrated in Table 1. Display differences are shown in Table 2.

Pin Connections

Pin Names

Discharge command

SNS

Sense resistor input

DCMD

DSEL

Display select

LED1

Charge status output 1

DCMD

INH

DSEL

DIS

VSEL

Voltage termination

LED2

Charge status output 2

VSEL

MOD

select

VSS

System ground

TM1

VCC

TM1

Timer mode select 1

VCC

5.0V ± 10% power

TM2

Timer mode select 2

VSS

MOD

Charge current control

TCO

LED2

TCO

Temperature cutoff

DIS

Discharge control

LED1

BAT

SNS

Temperature sense

output

BAT

Battery voltage

Charge inhibit input

INH

16-Pin Narrow DIP

or Narrow SOIC

PN2004E01.eps

SLU S081 - JU

NE 1999

bq2004E/H

Pin Descriptions


DCMD	Discharge-before-charge control input
	The			input controls the conditions
		DCMD
	that enable discharge-before-charge. DCMD
	is pulled up internally. A negative-going
	pulse on		DCMD		initiates a discharge to end-
	of-discharge voltage (EDV) on the BAT pin,
	followed by a new charge cycle start. Tying
	DCMD to ground enables automatic
	discharge-before-charge on every new charge
	cycle start.

DSEL	Display select input
	This three-state input configures the charge
	status display mode of the LED1 and LED2 out-
	puts and can be used to disable top-off and
	pulsed-trickle. See Table 2.

VSEL	Voltage termination select input
	This three-state input controls the voltage-
	termination technique used by the
	bq2004E/H. When high, PVD is active.
	When floating, -	V is used. When pulled low,
	both PVD and -	V are disabled.

TM1– Timer mode inputs

TM2

TM1 and TM2 are three-state inputs that configure the fast charge safety timer, voltage termination hold-off time, “top-off ”, and trickle charge control. See Table 1.

TCO	Temperature cut-off threshold input
	Input to set maximum allowable battery
	temperature. If the potential between TS
	and SNS is less than the voltage at the TCO
	input, then fast charge or top-off charge is ter-
	minated.

TS	Temperature sense input
	Input, referenced to SNS, for an external
	thermister monitoring battery temperature.
BAT	Battery voltage input
	BAT is the battery voltage sense input, refer-
	enced to SNS. This is created by a high-
	impedance resistor-divider network con-
	nected between the positive and the negative
	terminals of the battery.

SNS	Charging current sense input
	SNS controls the switching of MOD based on
	an external sense resistor in the current
	path of the battery. SNS is the reference po-
	tential for both the TS and BAT pins. If
	SNS is connected to VSS, then MOD switches
	high at the beginning of charge and low at
	the end of charge.

LED1–		Charge status outputs
LED2		Push-pull outputs indicating charging
		Push-pull outputs indicating charging
		status. See Table 2.
Vss		Ground
VCC		VCC supply input
		5.0V, ±10% power input.
MOD		Charge current control output
		MOD is a push-pull output that is used to
		control the charging current to the battery.
		MOD switches high to enable charging cur-
		rent to flow and low to inhibit charging
		current flow.
DIS		Discharge control output
		Push-pull output used to control an external
		transistor to discharge the battery before
		charging.
		Charge inhibit input
INH		Charge inhibit input
		When low, the bq2004E/H suspends all
		charge actions, drives all outputs to high im-
		pedance, and assumes a low-power opera-
		tional state. When transitioning from low to
		high, a new charge cycle is started.

bq2004E/H

Functional Description

Figure 2 shows a block diagram and Figure 3 shows a state diagram of the bq2004E/H.

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 two-cell potential for the battery under charge. A resistor-divider ratio of:

RB1 = N - 1

RB2 2

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.

Discharge-Before-Charge

The DCMD input is used to command discharge-before- charge via the DIS output. Once activated, DIS becomes active (high) until VCELL falls below VEDV, at which time DIS goes low and a new fast charge cycle begins.

The DCMD input is internally pulled up to VCC (its inactive state). Leaving the input unconnected, therefore, results in disabling discharge-before-charge. A negative going pulse on DCMD initiates discharge-before-charge at any time regardless of the current state of the bq2004. If DCMD is tied to VSS, discharge-before-charge will be the first step in all newly started charge cycles.

Starting A Charge Cycle

A new charge cycle is started by:

1.Application of VCC power.

2.VCELL falling through the maximum cell voltage, VMCV where:

Note: This resistor-divider network input impedance to end-to-end should be at least 200kΩ and less than 1MΩ.

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. Both the BAT and TS inputs are referenced to SNS, so the signals used inside the IC are:

VMCV = 0.8 VCC ± 30mV

3.A transition on the INH input from low to high.

If DCMD is tied low, a discharge-before-charge will be executed as the first step of the new charge cycle. Otherwise, pre-charge qualification testing will be the first step.

The battery must be within the configured temperature and voltage limits before fast charging begins.

VBAT - VSNS = VCELL

and

VTS - VSNS = VTEMP

The valid battery voltage range is VEDV < VBAT < VMCV where:

VEDV = 0.4 VCC ± 30mV

		Negative Temperature
		Coefficient Thermister
			VCC
			RT1	PACK +
		PACK+	RT1
		PACK+
bq2004E/H	RB1	TS		N
bq2004E/H	RB1	bq2004E/H	RT2	N
BAT		bq2004E/H		T
				T
				C
				C
	RB2	SNS
SNS		SNS		PACK -
		PACK-		PACK -
		PACK-

Fg2004a.eps

Figure 1. Voltage and Temperature Monitoring

UNITRODE bq2004E, bq2004H Technical data

bq2004E/H
		TM1 TM2		TCO
	OSC	Timing		TCO	TS
	OSC	Control		Check	TS
		Control		Check
LED1	Display			LTF
LED2	Display			LTF
LED2	Control			Check
DSEL	Control			Check
DSEL			VTS - VSNS
			VTS - VSNS	A/D
DCMD	Charge Control		VBAT - VSNS	A/D	SNS
DCMD	Charge Control
DVEN	State Machine			EDV
DVEN				EDV
				Check
	Discharge	MOD	PWR	MCV	BAT
	Control	Control	Control	Check	BAT
	Control	Control	Control	Check
	DIS	MOD	INH	VCC	VSS
					BD200401.eps

Figure 2. Block Diagram

The valid temperature range is VHTF < VTEMP < VLTF, where:

VLTF = 0.4 VCC ± 30mV

VHTF = [(1/3 VLTF) + (2/3 VTCO)] ± 30mV

VTCO is the voltage presented at the TCO input pin, and is configured by the user with a resistor divider between VCC

and ground. The allowed range is 0.2 to 0.4 VCC.

If the temperature of the battery is out of range, or the voltage is too low, the chip enters the charge pending state and waits for both conditions to fall within their allowed limits. During the charge-pending mode, the IC first applies a top-off charge to the battery.

The top-off charge, at the rate of 18 of the fast charge, continues until the fast-charge conditions are met or the top-off time-out period is exceeded. The IC then trickle charges until the fast-charge conditions are met. There is no time limit on the charge pending state; the charger remains in this state as long as the voltage or temperature conditons are outside of the allowed limits. If the voltage is too high, the chip goes to the battery absent state and waits until a new charge cycle is started.

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

Delta temperature/delta time ( T/ t)

Peak voltage detection (PVD)

Negative delta voltage (- V)

Maximum voltage

Maximum temperature

Maximum time

PVD and - V Termination

The bq2004E/H samples the voltage at the BAT pin once every 34s. When - V termination is selected, if VCELL is lower than any previously measured value by 12mV

±4mV (6mV/cell), fast charge is terminated. When PVD termination is selected, if VCELL is lower than any previously measured value by 6mV ±2mV (3mV/cell), fast charge is terminated. The PVD and - V tests are valid in the range 0.4 VCC < VCELL < 0.8 VCC.

bq2004E/H

VSEL Input	Voltage Termination
Low	Disabled
Float	- V
High	PVD

Voltage Sampling

Each sample is an average of voltage measurements. The IC takes 32 measurements in PVD mode and 16 measurements in - V mode. The resulting sample periods (9.17ms and 18.18ms, respectively) filter out harmonics centered around 55Hz and 109Hz. This technique minimizes the effect of any AC line ripple that may feed through the power supply from either 50Hz or 60Hz AC sources. Tolerance on all timing is ±16%.

Temperature and Voltage Termination

Hold-off

A hold-off period occurs at the start of fast charging. During the hold-off period, - V and T/ t termination are disabled. The MOD pin is enabled at a duty cycle of 260µs active for every 1820µs inactive. This modulation results in an average rate 1/8th that of the fast charge rate. This avoids premature termination on the voltage spikes sometimes produced by older batteries when fast-charge current is first applied. Maximum voltage and maximum temperature terminations are not affected by the hold-off period.

T/ t Termination

The bq2004E/H samples at the voltage at the TS pin every 34s, and compares it to the value measured two samples earlier. If VTEMP has fallen 16mV ±4mV or more, fast charge is terminated. The T/ t termination test is valid only when VTCO < VTEMP < VLTF.

Temperature Sampling

Each sample is an average of 16 voltage measurements. The resulting sample period (18.18ms) filters out harmonics around 55Hz. This technique minimizes the effect of any AC line ripple that may feed through the power supply from either 50Hz or 60Hz AC sources. Tolerance on all timing is ±16%.

Maximum Voltage, Temperature, and Time

Anytime VCELL rises above VMCV, the LEDs go off and current flow into the battery ceases immediately. If VCELL then falls back below VMCV before tMCV = 1.5s ±0.5s, the chip transitions to the Charge Complete state (maximum voltage termination). If VCELL remains above VMCV at the expiration of tMCV, the bq2004E/H transitions to the Battery Absent state (battery removal). See Figure 3.

Maximum temperature termination occurs anytime VTEMP falls below the temperature cutoff threshold VTCO. Charge will also be terminated if VTEMP rises above the low temperature fault threshold, VLTF, after fast charge begins.

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

Typical

Pulse-

Corresponding

Fast-Charge

PVD, - V

Fast-Charge

Safety

Hold-Off

Top-Off

Pulse-

Trickle

Rate

Time (min)

Time (s)

Rate

Period (Hz)

Trickle

2004E

2004H

2004E

2004H

2004E

2004H

2004E

2004H

2004E

2004H

TM1

TM2

Rate

C/4

C/8

Low

325

650

137

273

Disabled

C/2

C/4

Float

Low

154

325

546

Disabled

C/512

C/2

High

Low

154

273

546

Disabled

C/512

7.5

Low

Float

137

273

Disabled

C/512

3.75

7.5

Float

137

Disabled

C/512

1.88

3.75

C/2

C/4

High

Float

154

325

546

C/16

C/32

C/512

C/2

Low

High

154

273

546

C/8

C/16

C/512

7.5

Float

High

137

273

C/4

C/18

C/512

3.75

7.5

High

137

C/2

C/4

C/512

1.88

3.75

Note:

Typical conditions = 25°C, VCC = 5.0V.

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