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
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.
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 VCC 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
LED1–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.
When the temperature is valid, the bq2031 performs two
tests on the battery. In test 1, the bq2031 regulates a voltage
of VFLT + 0.25V across the battery and observes ISNS. If ISNS
does not rise to at least ICOND 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 ICOND (=
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 LED3, 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.
I
MAX/5) and watches VCELL (= VBAT - VSNS). If VCELL does
not rise to at least VFLT 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
Table 2. bq2031 Display Output Summary
Mode
Charge Action State
Battery absent or over-voltage fault
LED1
Low
LED2
LED3
Low
Low
Low
High
X
High
Low
Pre-charge qualification
Fast charging
Flash
High
Low
X
Low
DSEL = 0
(Mode 1)
Maintenance charging
Low
Charge pending (temperature out of range)
Charging fault
Flash
High
High
Low
X
X
Battery absent or over-voltage fault
Pre-charge qualification
Low
High
Low
High
X
Low
High
High
Low
X
Fast charge
Low
DSEL = 1
(Mode 2)
Maintenance charging
Low
Charge pending (temperature out of range)
Charging fault
Flash
High
High
Low
X
X
Battery absent or over-voltage fault
Pre-charge qualification
Low
Flash
Low
High
High
X
Low
Flash
High
High
Low
X
Fast charge: current regulation
Fast charge: voltage regulation
Maintenance charging
Low
DSEL = Float
(Mode 3)
Low
Low
Charge pending (temperature out of range)
Charging fault
Flash
High
X
X
1
1
Notes:
1 = VCC; 0 = VSS; X = LED state when fault occurred; Flash = 6 s low, 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.
4
TI [ TEXAS INSTRUMENTS ]
