BQ2954_13 Datasheet, PDF (6/23 Pages) Texas Instruments – Lithium Ion Charge Management IC

bq2954
Table 1. Normal Fast Charge Cycle
VBAT
IBAT
VREG
IMAX
VMIN
Battery
Absent
Qualification
Fast Charge
Current
Regulate
Voltage
Regulate
Current
Taper
IFULL
Detect
Charge
Complete
ICOND
IFULL
IMIN
Mode 1
(DSEL = 0)
Mode 2
(DSEL = 1)
Mode 3
(DSEL = F)
Mode 1
and 2
Mode 3
LED1
LED2
LED1
LED2
LED1
LED2
CHG
BTST
CHG
BTST
Low
Low
Low
Low
Low
Low
Low
High
Low
High
High
Low
High
Low
High
Low
High
Low
High
High
Time
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
Low
High
High
High
Low
High
Low
MTO
Low
High
Low
High
Low
High
High
Low
High
Low
Low
High
Low
High
Low
High
Low
Low
Low
Low
GR295401.eps
time-out limit t_QT (i.e., the battery has failed short), the
bq2954 enters the Fault state. Then t_QT is set to 25% of
t_MTO. If V_MIN is achieved before expiration of the time
limit, the bq2954 begins fast charging.
Once in the Fault state, the bq2954 waits until V_CC is cy-
cled or a new battery insertion is detected. It then starts a
new charge cycle and begins the qualification process again.
Charge Status Display
Charge status is indicated by the LED driver outputs
LED₁–LED₂. Three display modes (Tables 1– 3) are avail-
able in the bq2954 and are selected by configuring pin
DSEL. Table 1 illustrates a normal fast charge cycle, Ta-
ble 2 a recharge-after-fast-charge cycle, and Table 3 an ab-
normal condition.
Configuring the Display Mode, I_FULL/I_MIN,
and I_SENSE
DSEL/LED2 and CSEL/LED1 are bi-directional pins
with two functions: as LED driver pins (output) and as
programming pins (input). The selection of pull-up,
pull-down, or no-resistor programs the display mode on
DSEL as shown in Tables 1 through 3. A pull-down or
no-resistor programs the current-sense mode on CSEL.
The bq2954 latches the programming data sensed on
the DSEL and CSEL input when V_CC rises to a valid
level. The LEDs go blank for approximately 400ms (typi-
cal) while new programming data are latched.
When fast charge reaches a condition where the charg-
ing current drops below I_FULL, the LED1 and LED2
outputs indicate a full-battery condition. Fast charge
terminates when the charging current drops below the
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