Texas Instruments DV2031S2, BQ2031SN-A5, BQ2031PN-A5, BQ2031SN-A5TR Datasheet
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,
∆
2
V, minimum 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, 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 constantvoltage charging)
■
Maximum time-out (MTO)
After bulk charging, the bq2031 provides temperature-compensated
maintenance (float) charging to
maintain battery capacity.
1
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
TS Temperature sense input
TPWM Regulator timebase input
1
PN203101.eps
16-Pin Narrow
DIP or SOIC
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LED2/DSEL
LED1/TSEL
MOD
V
CC
V
SS
COM
LED3/QSEL
TPWM
TMTO
FLOAT
BAT
VCOMP
ICOMP
IGSEL
SNS
TS
LED3/ Charge status output 3/
QSEL Charge algorithm select
input 1
COM Common LED output
V
SS
System ground
V
CC
5.0V±10% power
MOD Modulation control
output
LED
1
/ Charge status output 1/
TSEL Charge algorithm select
input 2
LED
2
/ Charge status output 2/
DSEL Display select input
Pin Connections
Pin Names
SLUS156–JUNE 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 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
MIN
for
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
SNS
, connected in series with the low
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.
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
1–3
. This output is
in a high-impedance state during initiali
zat ion 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
1–3
Charger display status 1–3 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
1–3
charge display modes. See Table 2.
TSEL Termination select input
With QSEL, selects the charge algorithm.
See Table 1.
V
CC
VCCsupply
5.0V, ± 10% power
V
SS
Ground
Functional Description
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
2
bq2031
n
Fast charge termination
n
Maintenance charging
n
Charge regulation
Charge Algorithms
Three charge algorithms are available in the bq2031:
n
Two-Step Voltage
n
Two-Step Current
n
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 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
3
flashing.
3
bq2031
Algorithm/State QSEL TSEL Conditions MOD Output
Two-Step Voltage
L H/L
Note 1
--
Fast charge, phase 1 while V
BAT<VBLK,ISNS=IMAX
Current regulation
Fast charge, phase 2 while I
SNS>IMIN,VBAT=VBLK
Voltage regulation
Primary termination I
SNS=IMIN
Maintenance V
BAT=VFLT
Voltage regulation
Two-Step Current
HL - -
Fast charge while V
BAT<VBLK,ISNS=IMAX
Current regulation
Primary termination V
BAT=VBLK
or
∆
2
V < -8mV
Note 2
Maintenance I
SNS
pulsed to average I
FLT
Fixed pulse current
Pulsed Current
HH - -
Fast charge while V
BAT<VBLK,ISNS=IMAX
Current regulation
Primary termination V
BAT=VBLK
Maintenance
I
SNS=IMAX
after V
BAT=VFLT
;
I
SNS
= 0 after V
BAT=VBLK
Hysteretic pulsed
current
Notes: 1. May be high or low, but do not float.
2. 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
@ V
FLT
+
0.25V
Bulk
Charge
Fault
LED3 = 1
MOD = 0
Charge
Pending
LED3 Flash
MOD = 0
Current
Regulation
@I
COND
Temperature Out
of Range or
Thermistor Absent
Temperature In
Range, Return
to Original State
V
CELL
< V
LCO
or
V
CELL
> V
HCO
V
CELL
V
LCO or
Fail:
t = t
QT1
or
V
CELL
> V
HCO
Present
V
LCO
< V
CELL
< V
HCO
I
SNS
< I
COND
V
CELL
< V
MIN
FG203101.eps
Test 1
V
CELL
V
HCO
PASS: I
SNS
I
COND
>
Test 2
PASS: V
CELL
V
MIN
>
Fast
Charge
V
CELL
< V
MIN
Termination
Fail:
t = t
QT2
or
V
CELL
< V
LCO or
V
CELL
> V
HCO
Absent
V
CELL
< V
LCO
or
V
CELL
> V
HCO
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
.IfI
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
(=
I
MAX
/5) and watches V
CELL
(= V
BAT-VSNS
). 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
CC
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
1
–LED3. 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
3
, 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.
4
bq2031
Mode Charge Action State LED
1
LED
2
LED
3
DSEL = 0
(Mode 1)
Battery absent or over-voltage fault Low Low High
Pre-charge qualification Flash Low Low
Fast charging High Low Low
Maintenance charging Low High Low
Charge pending (temperature out of range) X X Flash
Charging fault X X High
DSEL = 1
(Mode 2)
Battery absent or over-voltage fault Low Low High
Pre-charge qualification High High Low
Fast charge Low High Low
Maintenance charging High Low Low
Charge pending (temperature out of range) X X Flash
Charging fault X X High
DSEL = Float
(Mode 3)
Battery absent or over-voltage fault Low Low High
Pre-charge qualification Flash Flash Low
Fast charge: current regulation Low High Low
Fast charge: voltage regulation High High Low
Maintenance charging High Low Low
Charge pending (temperature out of range) X X Flash
Charging fault X X High
Notes: 1 = VCC; 0 = VSS; X = LED state when fault occurred; Flash =
1
6
s low,
1
6
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
5
bq2031
I
FLT
I
MIN
I
COND
I
MAX
Current
Voltage
V
MIN
V
FLT
V
BLK
Time
Phase 1
Fast Charge
Phase 2
Current
Voltage
Maintenance
Qualification
Figure 2. Two-Step Voltage Algorithm
I
COND
I
MAX
Current
Voltage
V
MIN
V
FLT
V
BLK
Time
Fast Charge
Maintenance
Qualification
Current
Voltage
Figure 3. Two-Step Current Algorithm
I
COND
I
MAX
Current
Voltage
V
MIN
V
FLT
V
BLK
Time
Fast Charge
Maintenance
Qualification
Current
Voltage
Figure 4. Pulsed Current Algorithm
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