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,

V, mini-

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

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, constant-
current, or pulsed-current charging.
The regulator frequency is set by an
external capacitor for design flexi-
bility. 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 un-
til the battery voltage is within con-
figured 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
t i m e r r u n s o u t a n d p l a c e s t h e
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
t h r e s h o l d s

a r e

t e m p e r a t u r e -

compensated.

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

Maximum voltage

Second difference of cell voltage

(

Minimum current (in constant-
voltage charging)

Maximum time-out (MTO)

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

Lead-Acid Fast-Charge IC

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

Temperature sense input

TPWM

Regulator timebase input

PN203101.eps

16-Pin Narrow

DIP or SOIC

LED2/DSEL

LED1/TSEL

MOD

VCC

VSS

COM

LED3/QSEL

TPWM

TMTO

FLOAT

BAT

VCOMP

ICOMP

IGSEL

SNS

LED

Charge status output 3/

QSEL

Charge algorithm select
input 1

COM

Common LED output

System ground

5.0V

±10% power

MOD

Modulation control
output

LED

Charge status output 1/

TSEL

Charge algorithm select
input 2

LED

Charge status output 2/

DSEL

Display select input

Pin Connections

Pin Names

SLUS156JUNE 1999 E

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

FLT

) for the float

charge regulation. See Figure 1.

BAT

Battery voltage input

BAT is the battery voltage sense input. This po-
tential is generally developed using a high-
impedance 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 net-
work for voltage loop stability.

IGSEL

Current gain select input

This three-state input is used to set I

MIN

for

fast charge termination in the Two-Step
Voltage algorithm and for maintenance cur-
rent regulation in the Two-Step Current al-
gorithm. 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

SNS

, connected in series with the low

side of the battery. See equation 8.

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.

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

in a high-impedance state during initiali-
zation to read program inputs on TSEL,
QSEL, and DSEL.

QSEL

Charge regulation select input

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

13

Charger display status 13 outputs

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

supply

5.0V,

± 10% power

Ground

Functional Description

The bq2031 functional operation is described in terms of:

Charge algorithms

Charge qualification

Charge status display

Voltage and current monitoring

Temperature monitoring

bq2031

Fast charge termination

Maintenance charging

Charge regulation

Charge Algorithms

Three charge algorithms are available in the bq2031:

Two-Step Voltage

Two-Step Current

Pulsed Current

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 qualifi-
cation and temperature monitoring. The bq2031 first
checks that the battery temperature is within the al-
lowed, 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 bat-
tery temperature is within the allowed range. Charge
Pending is annunciated by LED

flashing.

bq2031

Algorithm/State

QSEL

TSEL

Conditions

MOD Output

Two-Step Voltage

H/L

Note 1

Fast charge, phase 1

while V

BAT

< V

BLK

, I

SNS

= I

MAX

Current regulation

Fast charge, phase 2

while I

SNS

> I

MIN

, V

BAT

= V

BLK

Voltage regulation

Primary termination

SNS

= I

MIN

Maintenance

BAT

= V

FLT

Voltage regulation

Two-Step Current

Fast charge

while V

BAT

< V

BLK

, I

SNS

= I

MAX

Current regulation

Primary termination

BAT

= V

BLK

V < -8mV

Note 2

Maintenance

SNS

pulsed to average I

FLT

Fixed pulse current

Pulsed Current

Fast charge

while V

BAT

< V

BLK

, I

SNS

= I

MAX

Current regulation

Primary termination

BAT

= V

BLK

Maintenance

SNS

= I

MAX

after V

BAT

= V

FLT

;

SNS

= 0 after V

BAT

= V

BLK

Hysteretic pulsed

current

Notes:

May be high or low, but do not float.

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

BAT

Table 1. bq2031 Charging Algorithms

Chip On

VCC 4.5V

Temperature

Checks On

Battery

Status?

Temperature

in Range

Temperature Out

of Range or

Thermistor Absent

Voltage

Regulation

@ VFLT +

0.25V

Bulk

Charge

Fault

LED3 = 1

MOD = 0

Charge

Pending

LED3 Flash

MOD = 0

Current

Regulation

@ICOND

Temperature Out

of Range or

Thermistor Absent

Temperature In

Range, Return

to Original State

VCELL < VLCO or
VCELL > VHCO

VCELL VLCO or

Fail:
t = tQT1 or
VCELL > VHCO

Present

VLCO < VCELL < VHCO

ISNS < ICOND

VCELL < VMIN

FG203101.eps

Test 1

VCELL VHCO

PASS: ISNS ICOND

Test 2

PASS: VCELL VMIN

Fast

Charge

VCELL < VMIN

Termination

Fail:
t = tQT2 or
VCELL < VLCO or
VCELL > VHCO

Absent

VCELL < VLCO or

VCELL > VHCO

Figure 1. Cycle Start/Battery

Qualification State Diagram

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

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

FLT

+ 0.25V across the battery and observes I

SNS

. If I

SNS

does not rise to at least I

COND

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

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

COND

MAX

/5) and watches V

CELL

(= V

BAT

- V

SNS

). If V

CELL

does

not rise to at least V

FLT

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

has failed short), again the bq2031 enters the Fault state. A
hold-off period is enforced at the beginning of qualification

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

is cy-

cled or a battery insertion is detected. It then starts a new
charge cycle and begins the qualification process again.

Charge Status Display

Charge status is annunciated by the LED driver outputs
LED

LED

. Three display modes are available in the bq2031;

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

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

, when-

ever the battery is absent. The bq2031, therefore, gives an
indication that the charger is on even when no battery is
in place to be charged.

bq2031

Mode

Charge Action State

LED

DSEL = 0

(Mode 1)

Battery absent or over-voltage fault

Low

High

Pre-charge qualification

Flash

Low

Fast charging

High

Low

Maintenance charging

Low

High

Low

Charge pending (temperature out of range)

Flash

Charging fault

High

DSEL = 1

(Mode 2)

Battery absent or over-voltage fault

Low

High

Pre-charge qualification

High

Low

Fast charge

Low

High

Low

Maintenance charging

High

Low

Charge pending (temperature out of range)

Flash

Charging fault

High

DSEL = Float

(Mode 3)

Battery absent or over-voltage fault

Low

High

Pre-charge qualification

Flash

Low

Fast charge: current regulation

Low

High

Low

Fast charge: voltage regulation

High

Low

Maintenance charging

High

Low

Charge pending (temperature out of range)

Flash

Charging fault

High

Notes:

1 = V

; 0 = V

; X = LED state when fault occurred; Flash =

s low,

s high.

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

Table 2. bq2031 Display Output Summary

Configuring Algorithm and Display

Modes

QSEL/LED

, DSEL/LED

, and TSEL/LED

are bi-

directional 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:

rises to a valid level.

The bq2031 leaves the Fault state.

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

sense resistor (R

SNS

) between the negative terminal

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

bq2031

FG203103.eps

bq2031

LED1/TSEL

VCC

COM

LED3/QSEL

VCC

VSS

LED2/DSEL

10K

VSS

Figure 5. Configuring Charging Algorithm and Display Mode

FG203102.eps

bq2031

BAT

VCC

SNS

VCC

VSS

FLOAT

RB3

BAT -

RSNS

VSS

BAT +

RB1

RB2

Figure 6. Configuring the Battery Divider

The resistor values are calculated from the following:

Equation 1

RB1

RB2

FLT

(

)

2 2

Equation 2

RB1

RB2

RB1

RB3

(

)

BLK

2 2

Equation 3

MAX

SNS

0 250

where:

N = Number of cells

FLT

= Desired float voltage

BLK

= Desired bulk charging voltage

MAX

= Desired maximum charge current

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 1M

. 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 re-
sistor network is as follows:

Set RB2 to 49.9 k

. (for 3 to 18 series cells)

Determine RB1 from equation 1 given V

FLT

Determine RB3 from equation 2 given V

BLK

Calculate R

SNS

from equation 3 given I

MAX

Battery Insertion and Removal

The bq2031 uses V

BAT

to detect the presence or absence

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

BAT

is between the High-Voltage Cutoff

HCO

= 0.6 * V

) and the Low-Voltage Cutoff (V

LCO

0.8V). When V

BAT

is outside this range, the bq2031 de-

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

LCO

and V

HCO

are treated as battery inser-

tions and removals, respectively. Besides being used to
detect battery insertion, the V

HCO

limit implicitly serves

as an over-voltage charge termination, because exceed-
ing this limit causes the bq2031 to believe that the bat-
tery has been removed.

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

TEMP

)

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-
perature range in which charging is allowed. V

TCO

0.4 * V

H T F -- H i g h - t e m p e r a t u r e f a u l t -- T h r e s h o l d t o
which temperature must drop after temperature
cutoff is exceeded before charging can begin again.
V

HTF

= 0.44 * V

bq2031

FG203104.eps

VCC

VLTF = 0.6V

VHTF = 0.44V

VTCO = 0.4V

Hotter

VSS

TCO

HTF

LTF

Colder

Voltage

Temperature

Figure 7. Voltage Equivalent

of Temperature Thresholds

LTF--Low-temperature fault--Lower limit of the
temperature range in which charging is allowed. V

LTF

= 0.6 * V

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 6

0 250

(

)

(

)

(

)

RT1

RT2

LTF

Equation 5

0 44

(

)

(

)

RT1

RT2

HTF

where:

LTF

= thermistor resistance at LTF

HTF

= thermistor resistance at HTF

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

Disabling Temperature Sensing

Temperature sensing can be disabled by removing RT
and using a 100k

resistor 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 Two-
Step Voltage algorithm.

bq2031

FG203105.eps

bq2031

VCC

SNS

VCC

VSS

BAT -

RSNS

VSS

RT1

RT2

NTC
Thermistor

Figure 8. Configuring

Temperature Sensing

IGSEL

MIN

MAX

/10

MAX

/20

MAX

/30

Table 3. I

MIN

Termination Thresholds

Second Difference (

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

BAT

. The bq2031 takes a sample and makes a

termination decision at a frequency equal to 0.008 *
t

MTO

. Fast charge terminates when the accumulated dif-

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

BLK

. V

BLK

is set

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.

Hold-off Periods

Maximum V and

V termination criteria are subject

to a hold-off period at the start of fast charge equal to
0.15 * t

MTO

. During this time, these termination criteria

are ignored.

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 equa-
tion:

Equation 6

MTO

= 0.5 * R * C

where R is in k

, C is in µF, and t

MTO

is in hours. Typi-

cally, the maximum value for C of 0.1

µF 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 out-
of-range temperature (Charge Pending) state.

Maintenance Charging

Three algorithms are used in maintenance charging:

Two-Step Voltage algorithm

Two-Step Current algorithm

Pulsed Current algorithm

Two-Step Voltage Algorithm

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

FLT

. Charge current during maintenance is limited to

COND

Two-Step Current Algorithm

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

) of a

fixed current (I

COND

= I

MAX

/5) and duration (0.2 sec-

onds) pulse to achieve the configured average mainte-
nance current value. See Figure 10.

Maintenance current can be calculated by:

Equation 7

Maintenance current

COND

MAX

(( . )

)

(( .

)

0 2

0 04

where T

is the period of the waveform in seconds.

Table 4 gives the values of P programmed by IGSEL.

bq2031

FG203112.eps

VCC

VSS

bq2031

VSS

VCC

Figure 9. R-C Network for Setting MTO

Pulsed Current Algorithm

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

CELL

falls to V

FLT

. Full fast charge current (I

MAX

) is

then re-enabled to the battery until V

CELL

rises to V

BLK

This cycle repeats indefinitely.

Charge Regulation

The bq2031 controls charging through pulse-width modu-
lation of the MOD output pin, supporting both constant-
current 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 refer-
ence, and the MOD output modulated to maintain the de-
sired value.

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

SNS

, so nominal regulated current is set by:

Equation 8

MAX

= 0.250V/R

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

PWM

= 0.1/C

PWM

where C is in

µF and F is in kHz. A typical switching

rate is 100kHz, implying C

PWM

= 0.001

µF. MOD pulse

width is modulated between 0 and 80% of the switching
period.

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 topolo-
gies, contact the factory.

bq2031

IGSEL

(sec.)

0.4

0.8

1.6

Table 4. Fixed-Pulse Period by IGSEL

TD203101.eps

ICOND

IGSEL = L
Ave. Current

IGSEL = H
Ave. Current

IGSEL = Z
Ave. Current

TP = 1.6 Sec

TP = 0.8 Sec

TP = 0.4 Sec

0.2 Sec

Figure 10. Implementation of Fixed-Pulse Maintenance Charge

bq2031

Absolute Maximum Ratings

Symbol

Parameter

Minimum

Maximum

Unit

Notes

relative to V

-0.3

+7.0

DC voltage applied on any pin ex-
cluding V

relative to V

-0.3

+7.0

OPR

Operating ambient temperature

-20

+70

°C

Commercial

STG

Storage temperature

-55

+125

°C

SOLDER

Soldering temperature

+260

°C

10 s. max.

BIAS

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

(TA = TOPR; VCC = 5V

±10%)

Symbol

Parameter

Rating

Unit

Tolerance

Notes

REF

Internal reference voltage

2.20

= 25°C

Temperature coefficient

-3.9

mV/°C

10%

LTF

TS maximum threshold

0.6 * V

±0.03V

Low-temperature fault

HTF

TS hysteresis threshold

0.44 * V

±0.03V

High-temperature fault

TCO

TS minimum threshold

0.4 * V

±0.03V

Temperature cutoff

HCO

High cutoff voltage

0.60 * V

±0.03V

MIN

Under-voltage threshold at BAT

0.34 * V

±0.03V

LCO

Low cutoff voltage

0.8

±0.03V

SNS

Current sense at SNS

0.250

10%

MAX

0.05

10%

COND

bq2031

Recommended DC Operating Conditions

(TA = TOPR)

Symbol

Parameter

Minimum

Typical

Maximum

Unit

Notes

Supply voltage

4.5

5.0

5.5

TEMP

TS voltage potential

- V

SNS

CELL

Battery voltage potential

BAT

- V

SNS

Supply current

Outputs unloaded

DSEL tri-state open detection

-2

µA

Note 2

IGSEL tri-state open detection

-2

µA

Logic input high

-1.0

QSEL,TSEL

-0.3

DSEL, IGSEL

Logic input low

+1.0

QSEL,TSEL

+0.3

DSEL, IGSEL

LED

, LED

, output high

-0.8

10mA

MOD output high

-0.8

10mA

LED

, LED

, output low

+0.8V

10mA

MOD output low

+0.8V

10mA

FLOAT output low

+0.8V

5mA, Note 3

COM output low

SS+

0.5

30mA

LED

, LED

, source

-10

-0.5V

MOD source

-5.0

-0.5V

LED

, LED

, sink

= V

+0.5V

MOD sink

= V

+0.8V

FLOAT sink

= V

+0.8V, Note 3

COM sink

= V

+0.5V

DSEL logic input low source

+30

µA

V = V

to V

+ 0.3V, Note 2

IGSEL logic input low source

+70

µA

V = V

to V

+ 0.3V

DSEL logic input high source

-30

µA

V = V

- 0.3V to V

IGSEL logic input high source

-70

µA

V = V

- 0.3V to V

Input leakage

±1

µA

QSEL, TSEL, Note 2

Notes:

All voltages relative to V

except where noted.

Conditions during initialization after V

applied.

SNS = 0V.

bq2031

Impedance

Symbol

Parameter

Minimum

Typical

Maximum

Unit

Notes

BATZ

BAT pin input impedance

SNSZ

SNS pin input impedance

TSZ

TS pin input impedance

PROG1

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

DSEL, TSEL, and
QSEL

PROG2

Pull-up or pull-down resistor value

IGSEL

MTO

Charge timer resistor

480

Timing

(TA = TOPR; VCC = 5V

±10%)

Symbol

Parameter

Minimum

Typical

Maximum

Unit

Notes

MTO

Charge time-out range

hours

See Figure 9

QT1

Pre-charge qual test 1 time-out period

0.02t

MTO

QT2

Pre-charge qual test 2 time-out period

0.16t

MTO

V termination sample frequency

0.008t

MTO

H01

Pre-charge qual test 2 hold-off period

0.002t

MTO

H02

Bulk charge hold-off period

0.015t

MTO

PWM

PWM regulator frequency range

100

kHz

See Equation 9

Capacitance

Symbol

Parameter

Minimum

Typical

Maximum

Unit

MTO

Charge timer capacitor

0.1

µF

PWM

PWM R-C capacitance

0.001

µF

bq2031

16-Pin SOIC Narrow (SN)

.004

16-Pin SN (0.150" SOIC)

Dimension

Inches

Millimeters

Min.

Max.

Min.

Max.

0.060

0.070

1.52

1.78

0.004

0.010

0.10

0.25

0.013

0.020

0.33

0.51

0.007

0.010

0.18

0.25

0.385

0.400

9.78

10.16

0.150

0.160

3.81

4.06

0.045

0.055

1.14

1.40

0.225

0.245

5.72

6.22

0.015

0.035

0.38

0.89

16-Pin PN (0.300" DIP)

Dimension

Inches

Millimeters

Min.

Max.

Min.

Max.

0.160

0.180

4.06

4.57

0.015

0.040

0.38

1.02

0.015

0.022

0.38

0.56

0.055

0.065

1.40

1.65

0.008

0.013

0.20

0.33

0.740

0.770

18.80

19.56

0.300

0.325

7.62

8.26

0.230

0.280

5.84

7.11

0.300

0.370

7.62

9.40

0.090

0.110

2.29

2.79

0.115

0.150

2.92

3.81

0.020

0.040

0.51

1.02

16-Pin DIP Narrow (PN)

bq2031

Change No.

Page No.

Description

Nature of Change

Descriptions

Clarified and consolidated

Renamed

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

MCV

to V

HCO

INT

to V

LCO

UV1

to t

QT1

UV2

to t

QT2

Consolidation

Tables 1 and 2

Added figures

Start-up states
Temperature sense input voltage thresholds
Pulsed maintenance current implementation

Updated figures

Figures 1 through 6

Added equations

Thermistor divider network configuration equations

Raised condition

MOD V

and V

parameters from

5mA to 10µA

Corrected Conditions

VSNS rating from V

MAX

and V

MIN

to I

MAX

and I

MIN

Added table

Capacitance table for C

MTO

and C

PWM

Changed values in
Figure 5

Was 51K; is now 10K

7, 10

Changed values
in Equations 3 and 8

Was: I

MAX

= 0.275V/R

SNS

; is now I

MAX

= 0.250V/R

SNS

Changed values
in Equation 4

Was: (V

- 0.275); is now (V

- 0.250V)

Changed rating value
for V

SNS

in DC

Thresholds table

Was 0.275; is now 0.250

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.

Data Sheet Revision History

bq2031

Package Option:

= 16-pin plastic DIP

= 16-pin narrow SOIC

Device:

bq2031 Lead Acid Charge IC

Ordering Information

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