TEXAS INSTRUMENTS bq2031 Technical data

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bq2031

Lead-Acid Fast-Charge IC

Features

Conforms to battery manufactur

➤

ers' charge recommendations for
cyclic and float charge

Pin-selectable charge algorithms

➤

Two-Step Voltage with

-

temperature-compensated
constant-voltage maintenance

Two-Step Current with

-

constant-rate pulsed current
maintenance

Pulsed Current: hysteretic,

-

on-demand pulsed current

Pin-selectable charge termination

➤

by maximum voltage,
mum current, and maximum
time

➤ Pre-charge qualification detects

shorted, opened, or damaged cells
and conditions battery

➤ Charging continuously qualified by

temperature and voltage limits

➤ Internal temperature-compen-

sated voltage reference

➤ Pulse-width modulation control

2

V, mini-

∆

Ideal for high-efficiency

-

-

switch-mode power conversion

Configurable for linear or

-

gated current use

Direct LED control outputs dis

➤

play charge status and fault con
ditions

General Description

The bq2031 Lead-Acid Fast Charge
IC is designed to optimize charging
of lead-acid chemistry batteries. A
flexible pulse-width modulation
regulator allows the bq2031 to con
trol constant-voltage, constant­current, or pulsed-current charging.
The regulator frequency is set by an
external capacitor for design flexi­bility. The switch-mode design keeps
power dissipation to a minimum for
high charge current applications.

A charge cycle begins when power is
applied or the battery is replaced.
For safety, charging is inhibited un­til the battery voltage is within con­figured limits. If the battery voltage is
less than the low-voltage threshold,
the bq2031 provides trickle-current

charging until the voltage rises into
the allowed range or an internal
timer runs out and places the
bq2031 in a Fault condition. This
procedure prevents high-current
charging of cells that are possibly

­damaged or reversed. Charging is

­inhibited anytime the temperature

of the battery is outside the config
urable, allowed range. All voltage
thresholds are temperature­compensated.

The bq2031 terminates fast (bulk)
charging based on the following:

Maximum voltage

■

-

Second difference of cell voltage

■

2

(

V)

∆

Minimum current (in constant-

■

voltage charging)

Maximum time-out (MTO)

■

After bulk charging, the bq2031 pro­vides temperature-compensated
maintenance (float) charging to
maintain battery capacity.

-

Pin Connections

TMTO

FLOAT

BAT

VCOMP

ICOMP

IGSEL

SNS

TS

SLUS156–JUNE 1999 E

1

2

3

4

5

6

7

8

16-Pin Narrow

DIP or SOIC

PN203101.eps

16

15

14

13

12

11

10

9

LED2/DSEL

LED1/TSEL

MOD

V

CC

V

SS

COM

LED3/QSEL

TPWM

Pin Names

TMTO Time-out timebase input

FLOAT State control output

BAT Battery voltage input

VCOMP Voltage loop comp input

ICOMP Current loop comp input

IGSEL Current gain select input

SNS Sense resistor input

TS Temperature sense input

TPWM Regulator timebase input

1

LED3/ Charge status output 3/
QSEL Charge algorithm select

input 1

COM Common LED output

V

SS

V

CC

System ground

5.0V±10% power

MOD Modulation control

output

/ Charge status output 1/

LED

1

TSEL Charge algorithm select

input 2

LED

/ Charge status output 2/

2

DSEL Display select input

bq2031

Pin Descriptions

TMTO Time-out timebase input

This input sets the maximum charge time.
The resistor and capacitor values are deter
mined using equation 6. Figure 9 shows the
resistor/capacitor connection.

FLOAT Float state control output

This open-drain output uses an external re
sistor divider network to control the BAT in
put voltage threshold (V
charge regulation. See Figure 1.

BAT Battery voltage input

BAT is the battery voltage sense input. This po
tential is generally developed using a high­impedance resistor divider network connected
between the positive and the negative terminals
of the battery. See Figure 6 and equation 2.

VCOMP Voltage loop compensation input

This input uses an external C or R-C net­work for voltage loop stability.

IGSEL Current gain select input

This three-state input is used to set I
fast charge termination in the Two-Step
Voltage algorithm and for maintenance cur­rent regulation in the Two-Step Current al­gorithm. See Tables 3 and 4.

ICOMP Current loop compensation input

This input uses an external C or R-C net
work for current loop stability.

SNS Charging current sense input

Battery current is sensed via the voltage de
veloped on this pin by an external sense re
sistor, R

, connected in series with the low

SNS

side of the battery. See equation 8.

TS Temperature sense input

This input is for an external battery tem
perature monitoring thermistor or probe. An
external resistor divider network sets the
lower and upper temperature thresholds.
See Figures 7 and 8 and equations 4 and 5.

) for the float

FLT

MIN

TPWM Regulation timebase input

This input uses an external timing capacitor
to ground the pulse-width modulation
(PWM) frequency. See equation 9.

-

COM Common LED output

Common output for LED

. This output is

1–3

in a high-impedance state during initiali
zat ion to read program inputs on TSEL,

-

-

QSEL Charge regulation select input

QSEL, and DSEL.

With TSEL, selects the charge algorithm.
See Table 1.

MOD Current-switching control output

­MOD is a pulse-width modulated push/pull

output that is used to control the charging
current to the battery. MOD switches high
to enable current flow and low to inhibit cur
rent flow.

LED

Charger display status 1–3 outputs

1–3

These charger status output drivers are for
the direct drive of the LED display. Display
modes are shown in Table 2. These outputs are

for

tri-stated during initialization so that QSEL,
TSEL, and DSEL can be read.

DSEL Display select input

This three-level input controls the LED
charge display modes. See Table 2.

TSEL Termination select input

­With QSEL, selects the charge algorithm.

See Table 1.

V

CC

-

-

V

SS

Functional Description

-

VCCsupply

5.0V, ± 10% power

Ground

The bq2031 functional operation is described in terms of:

n

Charge algorithms

n

Charge qualification

n

Charge status display

n

Voltage and current monitoring

n

Temperature monitoring

-

-

1–3

2

Fast charge termination

n

Maintenance charging

n

Charge regulation

n

Charge Algorithms

Three charge algorithms are available in the bq2031:

Two-Step Voltage

n

Two-Step Current

n

Pulsed Current

n

The state transitions for these algorithms are described
in Table 1 and are shown graphically in Figures 2
through 4. The user selects a charge algorithm by con
figuring pins QSEL and TSEL.

Charge Qualification

The bq2031 starts a charge cycle when power is applied
while a battery is present or when a battery is inserted.
Figure 1 shows the state diagram for pre-charge qualifi­cation and temperature monitoring. The bq2031 first
checks that the battery temperature is within the al­lowed, user-configurable range. If the temperature is
out-of-range (or the thermistor is missing), the bq2031
enters the Charge Pending state and waits until the bat­tery temperature is within the allowed range. Charge
Pending is annunciated by LED

flashing.

3

bq2031

Chip On

VCC 4.5V

Temperature

Checks On

Temperature

COND

>

I

MIN

>

< V

COND

V

HCO

Voltage
Regulation
@ V

0.25V

Current
Regulation
@I

MIN

Charge

COND

Bulk

in Range

Battery

Status?

Fail:
t = t

or

QT1

V

> V

CELL

+

FLT

Termination

Present

V

< V

LCO

CELL

Test 1

I

< I

SNS

PASS: I

SNS

Test 2

V

< V

PASS: V

CELL

CELL

-

Figure 1. Cycle Start/Battery

Qualification State Diagram

Temperature Out

of Range or

Thermistor Absent

Absent

V

< V

or

CELL

LCO

V

> V

CELL

HCO

HCO

Fault
LED3 = 1
MOD = 0

V

V

CELL

LCO or

V

V

CELL

HCO

Fail:
t = t

or

QT2

V

< V

CELL

LCO or

V

> V

CELL

HCO

V

< V

CELL

LCO

V

> V

CELL

HCO

V

CELL

Charge
Pending

LED3 Flash

MOD = 0

Temperature Out

of Range or

or

< V

MIN

Fast

Charge

FG203101.eps

Thermistor Absent

Temperature In
Range, Return

to Original State

Table 1. bq2031 Charging Algorithms

Algorithm/State QSEL TSEL Conditions MOD Output

Two-Step Voltage

L H/L
Fast charge, phase 1 while V
Fast charge, phase 2 while I
Primary termination I
Maintenance V

Two-Step Current

HL - ­Fast charge while V
Primary termination V
Maintenance I

Pulsed Current

HH - ­Fast charge while V
Primary termination V

Maintenance

Notes: 1. May be high or low, but do not float.

2. A Unitrode proprietary algorithm for accumulating successive differences between samples of V

Note 1

--

BAT<VBLK,ISNS=IMAX

SNS>IMIN,VBAT=VBLK

SNS=IMIN

BAT=VFLT

BAT<VBLK,ISNS=IMAX

or

BAT=VBLK

pulsed to average I

SNS

∆

BAT<VBLK,ISNS=IMAX

BAT=VBLK

I

SNS=IMAX

I

SNS

after V

= 0 after V

3

2

V < -8mV

BAT=VFLT

BAT=VBLK

Note 2

FLT

Current regulation

Voltage regulation

Voltage regulation

Current regulation

Fixed pulse current

Current regulation

;

Hysteretic pulsed

current

BAT

.

bq2031

Thermal monitoring continues throughout the charge
cycle, and the bq2031 enters the Charge Pending state
anytime the temperature is out of range. (There is one
exception; if the bq2031 is in the Fault state—see be
low—the out-of-range temperature is not recognized un
til the bq2031 leaves the Fault state.) All timers are

test 2 before the bq2031 recognizes its “pass” criterion. If this
second test passes, the bq2031 begins fast (bulk) charging.

Once in the Fault state, the bq2031 waits until V

­cled or a battery insertion is detected. It then starts a new

­charge cycle and begins the qualification process again.

suspended (but not reset) while the bq2031 is in Charge
Pending. When the temperature comes back into range,
the bq2031 returns to the point in the charge cycle
where the out-of-range temperature was detected.

When the temperature is valid, the bq2031 performs two
tests on the battery. In test 1, the bq2031 regulates a voltage
of V

+ 0.25V across the battery and observes I

FLT

does not rise to at least I

within a time-out period (e.g.,

COND

SNS

.IfI

the cell has failed open), the bq2031 enters the Fault state. If
test 1 passes, the bq2031 then regulates current to I
I

/5) and watches V

MAX

not rise to at least V

(= V

CELL

within a time-out period (e.g., the cell

FLT

BAT-VSNS

). If V

COND

CELL

has failed short), again the bq2031 enters the Fault state. A

Charge Status Display

Charge status is annunciated by the LED driver outputs
LED

–LED3. Three display modes are available in the bq2031;

1

the user selects a display mode by configuring pin DSEL. Table
2 shows the three modes and their programming pins.

SNS

The bq2031 does not distinguish between an over-voltage
fault and a “battery absent” condition. The bq2031 enters
the Fault state, annunciated by turning on LED

(=

ever the battery is absent. The bq2031, therefore, gives an

does

indication that the charger is on even when no battery is
in place to be charged.

hold-off period is enforced at the beginning of qualification

Table 2. bq2031 Display Output Summary

Mode Charge Action State LED

Battery absent or over-voltage fault Low Low High

Pre-charge qualification Flash Low Low

DSEL = 0

(Mode 1)

Charge pending (temperature out of range) X X Flash

Battery absent or over-voltage fault Low Low High

DSEL = 1

(Mode 2)

Charge pending (temperature out of range) X X Flash

Battery absent or over-voltage fault Low Low High

Fast charge: current regulation Low High Low

DSEL = Float

(Mode 3)

Fast charge: voltage regulation High High Low

Charge pending (temperature out of range) X X Flash

Notes: 1 = VCC; 0 = VSS; X = LED state when fault occurred; Flash =

In the Pulsed Current algorithm, the bq2031 annunciates maintenance when charging current is off and
fast charge whenever charging current is on.

Fast charging High Low Low

Maintenance charging Low High Low

Charging fault X X High

Pre-charge qualification High High Low

Fast charge Low High Low

Maintenance charging High Low Low

Charging fault X X High

Pre-charge qualification Flash Flash Low

Maintenance charging High Low Low

Charging fault X X High

1

6

s low,

1

1

s high.

6

LED

is cy

-

CC

, when

-

3

2

LED

3

4

I

MAX

I

COND

I

MIN

I

FLT

I

MAX

I

COND

Current

Current

Voltage

Qualification

Phase 1

Fast Charge

Phase 2

Current

Time

Figure 2. Two-Step Voltage Algorithm

Current

Qualification

Fast Charge

Voltage

Maintenance

Maintenance

V

BLK

V

FLT

V

MIN

Voltage

V

BLK

V

FLT

V

MIN

Voltage

bq2031

I

MAX

I

COND

Current

Time

Figure 3. Two-Step Current Algorithm

Current

Qualification

Fast Charge

Voltage

Time

Figure 4. Pulsed Current Algorithm

5

Maintenance

V

BLK

V

FLT

V

MIN

Voltage

bq2031

Configuring Algorithm and Display
Modes

QSEL/LED3, DSEL/LED2, and TSEL/LED1are bi­directional pins with two functions; they are LED driver
pins as outputs and programming pins for the bq2031 as
inputs. The selection of pull-up, pull-down, or no pull re
sistor programs the charging algorithm on QSEL and
TSEL per Table 1 and the display mode on DSEL per
Table 2. The bq2031 latches the program states when
any of the following events occurs:

1. V

2. The bq2031 leaves the Fault state.

3. The bq2031 detects battery insertion.

The LEDs go blank for approximately 750ms (typical)
while new programming data is latched.

For example, Figure 5 shows the bq2031 configured for
the Pulsed Current algorithm and display mode 2.

Voltage and Current Monitoring

The bq2031 monitors battery pack voltage at the BAT
pin. A voltage divider between the positive and negative
terminals of the battery pack is used to present a scaled
battery pack voltage to the BAT pin and an appropriate
value for regulation of float (maintenance) voltage to the
FLOAT pin. The bq2031 also uses the voltage across a

rises to a valid level.

CC

V

CC

RB3

RB1

RB2

R

SNS

FG203102.eps

2

CC

SS

bq2031

FLOAT

BAT

SNS

3

7

-

13

V

12

V

V

SS

Figure 6. Configuring the Battery Divider

sense resistor (R
of the battery pack and ground to monitor current.
See Figure 6 for the configuration of this network.

) between the negative terminal

SNS

BAT +

BAT -

V

CC

LED2/DSEL

LED1/TSEL

LED3/QSEL

bq2031

V

CC

V

SS

COM

10K

16

15

13

12

11

10

V

SS

10K

1K

1K

1K

10K

FG203103.eps

Figure 5. Configuring Charging Algorithm and Display Mode

6

bq2031

The resistor values are calculated from the following:

Equation 1

NV

RB1
RB2

∗−()

=

V

.22

FLT

1

Equation 2

N

RB1

RB1

+=

RB2

RB3

∗−V

BLK

(

)

221.

Equation 3

V

0 250.

I

=

MAX

R

SNS

where:

N = Number of cells

n

V

= Desired float voltage

n

FLT

V

n

n

= Desired bulk charging voltage

BLK

I

= Desired maximum charge current

MAX

These parameters are typically specified by the battery
manufacturer. The total resistance presented across the
battery pack by RB1 + RB2 should be between 150k
and 1MΩ. The minimum value ensures that the divider
network does not drain the battery excessively when the
power source is disconnected. Exceeding the maximum
value increases the noise susceptibility of the BAT pin.

An empirical procedure for setting the values in the re­sistor network is as follows:

1. Set RB2 to 49.9 kΩ. (for 3 to 18 series cells)

2. Determine RB1 from equation 1 given V

3. Determine RB3 from equation 2 given V

4. Calculate R

from equation 3 given I

SNS

FLT

BLK

MAX

Battery Insertion and Removal

The bq2031 uses V
of a battery. The bq2031 determines that a battery is
present when V
(V

= 0.6*VCC) and the Low-Voltage Cutoff (V

HCO

0.8V). When V
termines that no battery is present and transitions to
the Fault state. Transitions into and out of the range
between V

LCO

tions and removals, respectively. Besides being used to
detect battery insertion, the V
as an over-voltage charge termination, because exceed
ing this limit causes the bq2031 to believe that the bat
tery has been removed.

to detect the presence or absence

BAT

is between the High-Voltage Cutoff

BAT

is outside this range, the bq2031 de

BAT

and V

are treated as battery inser

HCO

limit implicitly serves

HCO

LCO

The user must include a pull-up resistor from the posi
tive terminal of the battery stack to VDC (and a diode to
prevent battery discharge through the power supply
when the supply is turned off) in order to detect battery
removal during periods of voltage regulation. Voltage
regulation occurs in pre-charge qualification test 1 prior
to all of the fast charge algorithms, and in phase 2 of the
Two-Step Voltage fast charge algorithm.

Temperature Monitoring

The bq2031 monitors temperature by examining the
voltage presented between the TS and SNS pins (V
by a resistor network that includes a Negative Tempera
ture Coefficient (NTC) thermistor. Resistance variations
around that value are interpreted as being proportional
to the battery temperature (see Figure 7).

The temperature thresholds used by the bq2031 and
their corresponding TS pin voltage are:

TCO—Temperature cutoff—Higher limit of the tem

n

perature range in which charging is allowed. V

0.4*V

CC

HTF—High-temperature fault—Threshold to

n

which temperature must drop after temperature
cutoff is exceeded before charging can begin again.
V

= 0.44*V

Ω

HTF

Voltage

V

V

=

-

-

-

-

Figure 7. Voltage Equivalent

CC

Colder

LTF

HTF
TCO

HotterV

FG203104.eps

V

LTF

HTF

TCO

V

CC

= 0.6V

= 0.44V

= 0.4V

SS

of Temperature Thresholds

-

)

TEMP

-

-

=

TCO

Temperature

7

bq2031

LTF—Low-temperature fault—Lower limit of the

n

temperature range in which charging is allowed. V
= 0.6*V

CC

A resistor-divider network must be implemented that
presents the defined voltage levels to the TS pin at the
desired temperatures (see Figure 8).

The equations for determining RT1 and RT2 are:

Equation 4

0 250

(.)

−

VV

06

.

∗=

V

CC

CC

()

∗+

RT1 RT2 R

1

+

()

RT2 R

LTF

∗

LTF

Equation 5

044

.

=

+

1

1

∗+

RT1 RT2 R

()

RT2 R

()

HTF

∗

HTF

where:

R

n

n

= thermistor resistance at LTF

LTF

R

= thermistor resistance at HTF

HTF

TCO is determined by the values of RT1 and RT2. 1%
resistors are recommended.

LTF

V

CC

bq2031

13

V

CC

12

V

SS

7

SNS

8

TS

V

SS

RT1

RT2

R

SNS

FG203105.eps

NTC
Thermistor

RT

t

BAT -

Figure 8. Configuring

Temperature Sensing

Disabling Temperature Sensing

Temperature sensing can be disabled by removing RT
and using a 100kΩresistor for RT1 and RT2.

Temperature Compensation

The internal voltage reference used by the bq2031 for all
voltage threshold determinations is compensated for
temperature. The temperature coefficient is -3.9mV/°C,
normalized to 25°C. Voltage thresholds in the bq2031
vary by this proportion as ambient conditions change.

Fast-Charge Termination

Fast-charge termination criteria are programmed with
the fast charge algorithm per Table 1. Note that not all
criteria are applied in all algorithms.

Minimum Current

Fast charge terminates when the charging current drops
below a minimum current threshold programmed by the
value of IGSEL (see Table 3). This is used by the Two­Step Voltage algorithm.

Table 3. I

IGSEL I

8

Termination Thresholds

MIN

MIN

0I

1I

ZI

MAX

MAX

MAX

/10

/20

/30

bq2031

Second Difference (

2

V)

∆

Second difference is a Unitrode proprietary algorithm
that accumulates the difference between successive sam
ples of V

. The bq2031 takes a sample and makes a

BAT

termination decision at a frequency equal to 0.008
t

. Fast charge terminates when the accumulated dif

MTO

ference is≤-8mV. Second difference is used only in the
Two-Step Current algorithm, and is subject to a hold-off
period (see below).

Maximum Voltage

Fast charge terminates when V

CELL

V

≥

BLK.VBLK

per equation 2. Maximum voltage is used for fast charge
termination in the Two-Step Current and Pulsed Cur
rent algorithms, and for transition from phase 1 to
phase 2 in the Two-Step Voltage algorithm. This crite
rion is subject to a hold-off period.

is set

Hold-off Periods

Maximum V and
to a hold-off period at the start of fast charge equal to

0.15*t

. During this time, these termination criteria

MTO

are ignored.

2

V termination criteria are subject

∆

Maximum Time-Out

Fast charge terminates if the programmed MTO time is
reached without some other termination shutting off
fast charge. MTO is programmed from 1 to 24 hours by
an R-C network on TMTO (see Figure 9) per the equa­tion:

Equation 6

t

= 0.5*R*C

MTO

where R is in kΩ, C is inµF, and t
cally, the maximum value for C of 0.1µF is used.

Fast-charge termination by MTO is a Fault only in the
Pulsed Current algorithm; the bq2031 enters the Fault
state and waits for a new battery insertion, at which
time it begins a new charge cycle. In the Two-Step Volt
age and Two-Step Current algorithms, the bq2031 tran
sitions to the maintenance phase on MTO time-out.

The MTO timer starts at the beginning of fast charge. In
the Two-Step Voltage algorithm, it is cleared and re
started when the bq2031 transitions from phase 1 (cur
rent regulation) to phase 2 (voltage regulation). The
MTO timer is suspended (but not reset) during the out­of-range temperature (Charge Pending) state.

is in hours. Typi

MTO

V

CC

-

*

R

1

TM

-

C

-

-

bq2031

V

SS

V

CC

V

SS

FG203112.eps

13

12

Figure 9. R-C Network for Setting MTO

Maintenance Charging

Three algorithms are used in maintenance charging:

n Two-Step Voltage algorithm

n

Two-Step Current algorithm

n

Pulsed Current algorithm

Two-Step Voltage Algorithm

In the Two-Step Voltage algorithm, the bq2031 provides
charge maintenance by regulating charging voltage to
V

. Charge current during maintenance is limited to

FLT

-

I

.

COND

Two-Step Current Algorithm

Maintenance charging in the Two-Step Current Algo
rithm is implemented by varying the period (T

-

fixed current (I

-

onds) pulse to achieve the configured average mainte

COND=IMAX

nance current value. See Figure 10.

Maintenance current can be calculated by:

­Equation 7

-

Maintenance current

where T

is the period of the waveform in seconds.

P

Table 4 gives the values of P programmed by IGSEL.

/5) and duration (0.2 sec

I

∗

=

COND

T

=

P

T

∗(( . ) ) (( . ) )02 004

P

)ofa

P

I

MAX

-

-

-

9

bq2031

Table 4. Fixed-Pulse Period by IGSEL

IGSEL TP(sec.)

L 0.4

H 0.8

Z 1.6

Pulsed Current Algorithm

In the Pulsed Current algorithm, charging current is
turned off after the initial fast charge termination until
V

falls to V

CELL

then re-enabled to the battery until V

. Full fast charge current (I

FLT

CELL

MAX

rises to V

)is

BLK

This cycle repeats indefinitely.

Charge Regulation

The bq2031 controls charging through pulse-width modu­lation of the MOD output pin, supporting both constant­current and constant-voltage regulation. Charge current
is monitored by the voltage at the SNS pin, and charge
voltage by voltage at the BAT pin. These voltages are
compared to an internal temperature-compensated refer­ence, and the MOD output modulated to maintain the de­sired value.

I

COND

IGSEL = L
Ave. Current

I

COND

0

IGSEL = H
Ave. Current

0

TP = 0.4 Sec

TP = 0.8 Sec

Voltage at the SNS pin is determined by the value of re
sistor R

, so nominal regulated current is set by:

SNS

Equation 8

I

= 0.250V/R

MAX

SNS

The switching frequency of the MOD output is deter
mined by an external capacitor (CPWM) between the
pin TPWM and ground, per the following:

Equation 9

F

= 0.1/C

PWM

PWM

where C is inµF and F is in kHz. A typical switching
rate is 100kHz, implying C
width is modulated between 0 and 80% of the switching

.

period.

= 0.001µF. MOD pulse

PWM

To prevent oscillation in the voltage and current control
loops, frequency compensation networks (C or R-C) are
typically required on the VCOMP and ICOMP pins (respec
tively) to add poles and zeros to the loop control equations.
A software program, “CNFG2031,” is available to assist in
configuring these networks for buck type regulators. For
more detail on the control loops in buck topology, see the
application note, “Switch-Mode Power Conversion Using
the bq2031.” For assistance with other power supply topolo­gies, contact the factory.

0.2 Sec

-

-

-

I

COND

IGSEL = Z
Ave. Current

0

TP = 1.6 Sec

TD203101.eps

Figure 10. Implementation of Fixed-Pulse Maintenance Charge

10

Absolute Maximum Ratings

Symbol Parameter Minimum Maximum Unit Notes

bq2031

V

CC

V

T

T

OPR

T

STG

T

SOLDER

T

BIAS

VCCrelative to V

SS

DC voltage applied on any pin ex
cluding V

relative to V

CC

SS

-

-0.3 +7.0 V

-0.3 +7.0 V

Operating ambient temperature -20 +70 °C Commercial

Storage temperature -55 +125 °C

Soldering temperature - +260 °C 10 s. max.

Temperature under bias -40 +85 °C

Note: Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional opera

tion should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Expo
sure to conditions beyond the operational limits for extended periods of time may affect device reliability.

DC Thresholds (T

= T

A

OPR;VCC

= 5V±10%)

Symbol Parameter Rating Unit Tolerance Notes

V

V

V

V

V

V

V

V

REF

LTF

HTF

TCO

HCO

MIN

LCO

SNS

Internal reference voltage 2.20 V 1% TA= 25°C

Temperature coefficient -3.9 mV/°C 10%

TS maximum threshold 0.6*V

TS hysteresis threshold 0.44*V

TS minimum threshold 0.4*V

High cutoff voltage 0.60*V

Under-voltage threshold at BAT 0.34*V

CC

CC

CC

CC

CC

Low cutoff voltage 0.8 V

0.250 V 10% I

Current sense at SNS

0.05 V 10% I

V

V

V

V

V

0.03V Low-temperature fault

±

0.03V High-temperature fault

±

0.03V Temperature cutoff

±

0.03V

±

0.03V

±

0.03V

±

MAX

COND

-

-

11

bq2031

Recommended DC Operating Conditions (T

= T

A

OPR)

Symbol Parameter Minimum Typical Maximum Unit Notes

V

V

V

I

CC

I

IZ

V

V

V

V

I

OH

CC

TEMP

CELL

IH

IL

OH

OL

Supply voltage 4.5 5.0 5.5 V

TS voltage potential 0 - V

Battery voltage potential 0 - V

CC

CC

VVTS- V

VV

BAT

- V

SNS

SNS

Supply current - 2 4 mA Outputs unloaded

DSEL tri-state open detection -2 - 2

IGSEL tri-state open detection -2 2

V

-1.0 - - V QSEL,TSEL

Logic input high

Logic input low

CC

V

-0.3 - - V DSEL, IGSEL

CC

--V

--V

+1.0 V QSEL,TSEL

SS

+0.3 V DSEL, IGSEL

SS

LED1, LED2, LED3, output high VCC-0.8 - - V I

MOD output high V

-0.8 - - V I

CC

LED1, LED2, LED3, output low - - VSS+0.8V V I

MOD output low - - V

FLOAT output low - - V

COM output low - - V

+0.8V V I

SS

+0.8V V I

SS

0.5 V I

SS+

A Note 2

µ

A

µ

OH

OH

OL

OL

OL

OL

10mA

≤

10mA

≤

10mA

≤

10mA

≤

5mA, Note 3

≤

30mA

≤

LED1, LED2, LED3, source -10 - - mA VOH=VCC-0.5V

MOD source -5.0 - - mA V

OH=VCC

-0.5V

LED1, LED2, LED3, sink 10 - - mA VOL= VSS+0.5V

I

OL

MOD sink 5 - - mA V

FLOAT sink 5 - - mA V

COM sink 30 - - mA V

I

IL

I

IH

I

L

DSEL logic input low source - - +30

IGSEL logic input low source - - +70

DSEL logic input high source -30 - -

IGSEL logic input high source -70 - -

Input leakage - -

±

1

A V = VSSto VSS+ 0.3V, Note 2

µ

A V = V

µ

A V = VCC- 0.3V to V

µ

A V = VCC- 0.3V to V

µ

A QSEL, TSEL, Note 2

µ

= VSS+0.8V

OL

= VSS+0.8V, Note 3

OL

= VSS+0.5V

OL

to VSS+ 0.3V

SS

Notes: 1. All voltages relative to VSSexcept where noted.

2. Conditions during initialization after V

applied.

CC

3. SNS = 0V.

CC

CC

12

bq2031

Impedance

Symbol Parameter Minimum Typical Maximum Unit Notes

R

BATZ

R

SNSZ

R

TSZ

R

PROG1

R

PROG2

R

MTO

Timing (T

BAT pin input impedance 50 - - M

SNS pin input impedance 50 - - M

TS pin input impedance 50 - - M

Soft-programmed pull-up or pull-down
resistor value (for programming)

--10

Pull-up or pull-down resistor value - - 3 k

Charge timer resistor 20 - 480 k

= T

A

OPR;VCC

= 5V±10%)

Ω

Ω

Ω

DSEL, TSEL, and

k

Ω

QSEL

IGSEL

Ω

Ω

Symbol Parameter Minimum Typical Maximum Unit Notes

t

t

t

t

t

t

F

MTO

QT1

QT2

DV

H01

H02

PWM

Charge time-out range 1 - 24 hours See Figure 9

Pre-charge qual test 1 time-out period - 0.02t

Pre-charge qual test 2 time-out period - 0.16t

2

V termination sample frequency - 0.008t

∆

Pre-charge qual test 2 hold-off period - 0.002t

Bulk charge hold-off period - 0.015t

MTO

MTO

MTO

MTO

MTO

--

--

--

--

--

PWM regulator frequency range - 100 kHz See Equation 9

Capacitance

Symbol Parameter Minimum Typical Maximum Unit

C

C

MTO

PWM

Charge timer capacitor - 0.1 0.1

PWM R-C capacitance - 0.001 -

13

F

µ

F

µ

bq2031

16-Pin DIP Narrow (PN)

16-Pin SOIC Narrow (SN)

D

e

E

H

C

A

A1

B

.004

16-Pin PN(0.300" DIP

Dimension

A 0.160 0.180 4.06 4.57

A1 0.015 0.040 0.38 1.02

B 0.015 0.022 0.38 0.56

B1 0.055 0.065 1.40 1.65

C 0.008 0.013 0.20 0.33

D 0.740 0.770 18.80 19.56

E 0.300 0.325 7.62 8.26

E1 0.230 0.280 5.84 7.11

e 0.300 0.370 7.62 9.40

G 0.090 0.110 2.29 2.79

L 0.115 0.150 2.92 3.81

S 0.020 0.040 0.51 1.02

Inches Millimeters

Min. Max. Min. Max.

16-Pin SN(0.150" SOIC

Dimension

A 0.060 0.070 1.52 1.78

A1 0.004 0.010 0.10 0.25

B 0.013 0.020 0.33 0.51

C 0.007 0.010 0.18 0.25

D 0.385 0.400 9.78 10.16

E 0.150 0.160 3.81 4.06

e 0.045 0.055 1.14 1.40

H 0.225 0.245 5.72 6.22

L 0.015 0.035 0.38 0.89

Inches Millimeters

Min. Max. Min. Max.

)

)

L

14

Data Sheet Revision History

Change No. Page No. Description Nature of Change

1 Descriptions Clarified and consolidated

Dual-Level Constant Current Mode to Two-Step Current Mode
V

to V

MCV

1 Renamed

V
t
t

INT

UV1

UV2

1 Consolidation Tables 1 and 2

Start-up states

1 Added figures

Temperature sense input voltage thresholds
Pulsed maintenance current implementation

1 Updated figures Figures 1 through 6

1 Added equations Thermistor divider network configuration equations

1 Raised condition MOD V

1 Corrected Conditions VSNS rating from V

1 Added table Capacitance table for C

26

3 7, 10

38

Changed values in
Figure 5

Changed values
in Equations 3 and 8

Changed values
in Equation 4

Was 51K; is now 10K

Was: I

Was: (V

Changed rating value

311

for V

SNS

in DC

Was 0.275; is now 0.250

Thresholds table

411T

OPR

Deleted industrial temperature range.

Notes: Change 1 = Dec. 1995 B changes from June 1995 A.

Change 2 = Sept. 1996 C changes from Dec. 1995 B.
Change 3 = April 1997 D changes from Sept. 1996 C.
Change 4 = June 1999 E changes from April 1997 D.

HCO

to V

LCO

to t

QT1

to t

QT2

and VOHparameters from≤5mA to≤10µA

OL

and V

MAX

MTO

= 0.275V/R

MAX

- 0.275); is now (VCC- 0.250V)

CC

; is now I

SNS

MIN

and C

to I

PWM

MAX

and I

MAX

= 0.250V/R

bq2031

MIN

SNS

Ordering Information

bq2031

Package Option:

PN = 16-pin plastic DIP
SN = 16-pin narrow SOIC

Device:

bq2031 Lead Acid Charge IC

15

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16