UNITRODE bq2005 Technical data

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BQ2005

Features

Sequential fast charge and conditioning of two NiCd or NiMH nickel cadmium or nickel-metal hydride battery packs

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

Direct LED outputs display battery and charge status

Fast-charge termination by

∆ temperature/∆ time, -∆V, maximum voltage, maximum temperature, and maximum time

Optional top-off and pulsetrickle charging

bq2005

Fast-Charge IC for Dual-Battery Packs

General Description

The bq2005 Fast-Charge IC provides comprehensive fast charge control functions together with high-speed switching power control circuitry on a monolithic CMOS device for sequential charge management in dual battery pack applications.

Integration of closed-loop current control circuitry allows the bq2005 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 bq2005-based chargers to support battery conditioning and capacity determination.

High-efficiency power conversion is accomplished using the bq2005 as a hysteretic PWM controller for switch-mode regulation of the charging current. The bq2005 may alterna-

tively 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 temperature 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)

Negative delta voltage (-∆V)

Maximum voltage

Maximum temperature

Maximum time

After fast charge, optional top-off and pulsed current maintenance phases are available.

Pin Connections

DCMDA

1

20

 

FCCB

DVEN

2

19

 

 

 

CHB

TM1

3

18

 

MODB

TM2

4

17

 

MODA

TCO

5

16

 

VCC

TSA

6

15

 

VSS

TSB

7

14

 

FCC

A

BATA

8

13

 

CH

A

BATB

9

12

 

DISA

SNSA

10

11

 

SNSB

20-Pin DIP or SOIC

PN200501.eps

SLUS079–JUNE 1999 F

Pin Names

 

 

 

 

 

 

 

 

DCMDA

Discharge command input,

DISA

Discharge control output,

 

 

battery A

 

 

 

 

battery A

DVEN

-∆V enable

 

 

 

 

 

CHA,

Charge status output,

 

 

 

 

 

 

 

 

 

 

CHB

battery A/B

TM1

Timer mode select 1

 

 

 

 

 

 

 

 

FCCA,

Fast charge complete output,

TM2

Timer mode select 2

 

 

 

 

 

FCCB

battery A/B

 

 

 

TCO

Temperature cut-off

VSS

System ground

 

 

 

TSA,

Temperature sense input,

VCC

5.0V ±10% power

TSB

battery A/B

 

 

 

 

 

 

 

 

MODA, Charge current control

BATA,

Battery voltage input,

MODB

output, battery A/B

 

 

 

BATB

battery A/B

 

 

 

 

 

SNSA,

Sense resistor input ,

 

 

 

 

 

SNSB

battery A/B

 

 

 

 

 

1

bq2005

Pin Descriptions

DCMDA

Discharge-before-charge control input,

 

battery A

 

 

A controls the discharge-before-charge

 

DCMD

 

function of the bq2005. A negative-going

 

pulse on DCMDA initiates a discharge to

 

EDV followed by a charge if conditions allow.

 

By tying DCMDA to ground, automatic

 

discharge-before-charge is enabled on every

 

new charge cycle start.

DVEN

-∆V enable input

 

This input enales/disables -V charge termina-

 

tion. If DVEN is high, the -V test is enabled.

 

If DVEN is low, -V test is disabled. The state

 

of DVEN may be changed at any time.

TM1

Timer mode inputs

TM2

TM1 and TM2 are three-state inputs that con-

 

 

figure the fast charge safety timer, -V hold-

 

off time, and that enhance/disable top-off.

 

See Table 2.

TCO

Temperature cutoff threshold input

 

Input to set maximum allowable battery

 

temperature. If the potential between TSA

 

and SNSA or TSB and SNSB is less than the

 

voltage at the TCO input, then fast charge or

 

top-off charge is terminated for the corre-

 

sponding battery pack.

TSA,

Temperature sense inputs

TSB

Input, referenced to SNSA or SNSB, respec-

 

 

tively, for an external thermistor monitoring

 

battery temperature.

BATA,

Voltage inputs

BATB

The battery voltage sense input, referenced to

 

 

SNSA,B, respectively. This is created by a

 

high-impedance resistor divider network con-

 

nected between the positive and the negative

 

terminals of the battery.

SNSA,

Charging current sense inputs,

SNSB

SNSA,B controls the switching of MODA,B

 

 

based on the voltage across an external

 

sense resistor in the current path of the bat-

 

tery. SNS is the reference potential for the

 

TS and BAT pins. If SNS is connected to

 

VSS, MOD switches high at the beginning of

 

charge and low at the end of charge.

DISA

Discharge control output

 

Push-pull output used to control an external

 

transistor to discharge battery A before

 

charging.

CHA, Charge status outputs

CHB

Push-pull outputs indicating charging status for batteries A and B, respectively. See Figure 1 and Table 2.

FCCA, Fast charge complete outputs

FCCB

Open-drain outputs indicating fast charge complete for batteries A and B, respectively. See Figure 1 and Table 2.

MODA, Charge current control outputs MODB

 

MODA,B is a push-pull output that is used to

 

control the charging current to the battery.

 

MODA,B switches high to enable charging

 

current to flow and low to inhibit charging

 

current flow to batteries A and B,

 

respectively.

VCC

VCC supply input

 

5.0 V, ±10% power input.

Vss

Ground

2

UNITRODE bq2005 Technical data

bq2005

Functional Description

Figure 3 shows a block diagram and Figure 4 shows a state diagram of the bq2005.

Battery Voltage and Temperature

Measurements

Discharge-Before-Charge

The DCMDA input is used to command discharge- before-charge via the DISA output. Once activated,

DISA becomes active (high) until VCELL falls below VEDV where:

VEDV = 0.475 VCC ± 30mV

Battery voltage and temperature are monitored for maximum allowable values. The voltage presented on the battery sense input, BATA,B, must be divided down to between 0.95 VCC and 0.475 VCC for proper operation. A resistor-divider ratio of:

 

RB1

=

N

1

 

RB2

2.375

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 200kand less than 1M.

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 TSA,B is developed using a resistor-thermistor network between VCC and VSS. See Figure 1. Both the BATA,B and TSA,B inputs are referenced to SNSA,B, so the signals used inside the IC are:

VBAT(A,B) - VSNS(A,B) = VCELL(A,B)

at which time DISA goes low and a new fast charge cycle begins.

The DCMDA 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 DCMDA initiates discharge-before-charge at any time regardless of the current state of the bq2005. If DCMDA 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 (see Figure 2):

1.VCC rising above 4.5V

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

VMCV = 0.95 VCC ± 30mV

If DCMDA 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

and voltage limits before fast charging begins.

 

 

VTS(A,B) - VSNS(A,B) = VTEMP(A,B)

 

 

 

 

 

Negative Temperature

 

 

 

Coefficient Thermister

 

 

 

 

VCC

 

 

 

 

RT1

PACK +

 

 

PACK+

 

 

 

 

 

bq2005

RB1

TSA,B

 

N

bq2005

RT2

BATA,B

 

T

 

 

 

 

 

C

 

RB2

SNSA,B

 

 

SNSA,B

 

 

PACK -

 

PACK-

 

 

Fg2005-1.eps

Figure 1. Voltage and Temperature Monitoring

3

bq2005

The valid battery voltage range is VEDV < VBAT < VMCV. The valid temperature range is VHTF < VTEMP < VLTF, where:

VLTF = 0.4 VCC ± 30mV

VHTF = [(1/4 VLTF) + (3/4 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. The MODA,B output is modulated to provide the configured trickle charge rate in the charge pending state. 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 five possible termination conditions:

Delta temperature/delta time (∆T/∆t)

Negative delta voltage (-∆V)

Maximum voltage

Maximum temperature

Maximum time

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dis-

 

 

Charge

 

 

Fast Charging

 

 

 

 

Top-Off

 

 

 

 

Pulse-Trickle

 

 

 

 

 

 

charge

 

 

Pending*

 

 

 

 

 

 

 

 

 

 

 

 

 

(Optional)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(Optional

(Pulse-Trickle)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Battery A)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DISA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MODA,B

 

Switch-mode

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4s

 

 

 

 

 

260 s

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Configuration

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

34s

 

 

 

 

 

 

 

 

 

 

Note*

 

 

 

 

 

or

 

External

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4s

 

 

 

 

 

 

 

260 s

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MODA,B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Regulation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

34s

 

 

 

 

 

 

 

Note*

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CH

A,B Status Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Status Output

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FCC

A,B

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Battery within temperature/voltage limits.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Battery discharged to 0.475

* VCC. Battery outside

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

temperature/voltage limits.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Discharge-Before-Charge started

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

*See Table 3 for pulse-trickle period.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

T200501.eps

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2. Charge Cycle Phases

4

 

 

 

 

 

 

bq2005

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Typical Fast-Charge

Typical -V/MCV

 

 

 

 

Corresponding

 

 

and Top-Off

Hold-Off

 

Top-Off

Fast-Charge Rate

TM1

TM2

Time Limits

Time (seconds)

 

Rate

 

C/4

Low

Low

360

137

 

Disabled

 

C/2

Float

Low

180

820

 

Disabled

 

1C

High

Low

90

410

 

Disabled

 

2C

Low

Float

45

200

 

Disabled

 

4C

Float

Float

23

100

 

Disabled

 

C/2

High

Float

180

820

 

C/16

 

1C

Low

High

90

410

 

C/8

 

2C

Float

High

45

200

 

C/4

 

4C

High

High

23

100

 

C/2

Note:

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

 

 

 

 

 

-V Termination

If the DVEN input is high, the bq2005 samples the voltage at the BAT pin once every 34s. If VCELL is lower than any previously measured value by 12mV ±4mV, fast charge is terminated. The -∆V test is valid in the range VMCV - (0.2 VCC) < VCELL < VMCV.

Voltage Sampling

Each sample is an average of 16 voltage measurements taken 57 s apart. 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%.

Voltage Termination Hold-off

A hold-off period occurs at the start of fast charging. During the hold-off period, -∆V termination is disabled. This avoids premature termination on the voltage spikes

sometimes produced by older batteries when fast-charge current is first applied. ∆T/∆t, maximum voltage and

maximum temperature terminations are not affected by the hold-off period.

T/t Termination

The bq2005 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 taken 57 s apart. 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, CHG goes high (the LED goes off) immediately. If the bq2005 is not in the voltage hold-off period, fast charging also ceases immediately. If VCELL then falls back below VMCV before tMCV = 1s (maximum), the chip transitions to the Charge Complete state (maximum voltage termination). If VCELL remains above VMCV at the expiration of tMCV, the bq2005 transitions to the Battery Absent state (battery removal). See Figure 4.

Maximum temperature termination occurs anytime the voltage on the TS pin falls below the temperature cut-off threshold VTCO. Charge will also be terminated if VTEMP rises above the minimum temperature fault threshold, VLTF, after fast charge begins.

Maximum charge time is configured using the TM pin. Time settings are available for corresponding charge rates of C/4, C/2, 1C, and 2C. Maximum time-out termination is enforced on the fast-charge phase, then reset, and enforced again on the top-off phase, if selected. There is no time limit on the trickle-charge phase.

Top-off Charge

An optional top-off charge phase may be selected to follow fast charge termination for the C/2 through 4C rates. This phase may be necessary on NiMH or other

5

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