bq2031
n
n
n
Fast charge termination
Maintenance charging
Charge regulation
Chip On
4.5V
V
CC
Temperature Out
of Range or
Thermistor Absent
Temperature
Checks On
Charge Algorithms
Three charge algorithms are available in the bq2031:
Temperature
in Range
Absent
Present
V
V
< V
CELL
or
HCO
CELL
LCO
> V
V
< V
< V
LCO
CELL HCO
Battery
Status?
Test 1
n
n
n
Two-Step Voltage
Two-Step Current
Pulsed Current
Fail:
t = t
CELL
I
< I
SNS COND
or
QT1
> V
HCO
V
Voltage
Fault
Regulation
@ V
LED3 = 1
MOD = 0
+
FLT
0.25V
V
CELL
V
LCO or
V
CELL
V
HCO
>
PASS: I
I
SNS COND
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.
Test 2
Fail:
t = t
or
QT2
V
< V
MIN
CELL
V
CELL
CELL
< V
LCO or
HCO
Current
Regulation
V
> V
Charge
Pending
LED3 Flash
MOD = 0
@I
COND
Temperature Out
>
of Range or
Thermistor Absent
PASS: V
V
MIN
CELL
Charge Qualification
V
CELL
V
CELL
< V
> V
or
LCO
HCO
Temperature In
Range, Return
to Original State
Bulk
Charge
Fast
Charge
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 LED3 flashing.
Termination
V
CELL
< V
MIN
FG203101.eps
Figure 1. Cycle Start/Battery
Qualification State Diagram
Table 1. bq2031 Charging Algorithms
Algorithm/State
QSEL
TSEL
H/LNote 1
Conditions
MOD Output
Two-Step Voltage
Fast charge, phase 1
Fast charge, phase 2
Primary termination
Maintenance
L
-
-
while VBAT < VBLK, ISNS = IMAX
while ISNS > IMIN, VBAT = VBLK
Current regulation
Voltage regulation
I
SNS = IMIN
VBAT = VFLT
Voltage regulation
Two-Step Current
Fast charge
Primary termination
Maintenance
Pulsed Current
Fast charge
H
H
L
-
-
while VBAT < VBLK, ISNS = IMAX
Current regulation
V
BAT = VBLK or ∆2V < -8mVNote 2
ISNS pulsed to average IFLT
-
Fixed pulse current
H
-
while VBAT < VBLK, ISNS = IMAX
Current regulation
Primary termination
V
BAT = VBLK
ISNS = IMAX after VBAT = VFLT
SNS = 0 after VBAT = VBLK
;
Hysteretic pulsed
current
Maintenance
I
Notes:
1. May be high or low, but do not float.
2. A Unitrode proprietary algorithm for accumulating successive differences between samples of VBAT
.
3
TI [ TEXAS INSTRUMENTS ]
