Datasheet

bq24401
www.ti.com SLUS497A –SEPTEMBER 2001–REVISED MARCH 2010
Table 3. Temperature-Monitoring Conditions and Actions (continued)
TEMPERATURE CONDITION ACTION
During charge qualification, stops charging
During fast charge, no effect
Hot battery – checked at all times,
V
TS
< V
HTF
except during fast charge
During top-off, stops charging
During trickle maintenance charge, stops charging
During charge qualification, stops charging
During fast charge, terminates fast charge and stops charging, turns off
Battery exceeding maximum
LED
V
TS
< V
TCO
allowable temperature – checked at
all times
During top-off, terminates top-off and stops charging
During trickle maintenance charge, stops charging
Table 4. Summary of NiCd or NiMH Charging Characteristics
PARAMETER VALUE
(1)
Maximum cell voltage (V
MCV
) 2 V
Minimum pre-charge qualification voltage (V
LBAT
) 950 mV
High-temperature cutoff voltage (V
TCO
) 0.225 × V
CC
High-temperature fault voltage (V
HTF
) 0.25 × V
CC
Low-temperature fault voltage (V
LTF
) 0.5 × V
CC
bq24401 fast-charge maximum time out (MTO) R
MTO
× C
MTO
× 35,988
Fast-charge charging current (I
MAX
) 0.05/R
SNS
Hold-off period MTO/32
Top-off charging current (optional) I
MAX
/16
Top-off period (optional) MTO
Trickle-charge frequency 1Hz
Trickle-charge pulse-width See Figure 5
(1) See the DC Thresholds Specification for details.
Charge Status Display
The charge status is indicated by open-drain output LED. Table 5 summarizes the display output of the bq24401.
A temperature fault or timer expiring changes the charge state immediately (according to Figure 2) and will thus
change the LED status immediately and accordingly.
Table 5. Charge Status Display
bq24401 CHARGE STATE LED STATUS
Charge qualification (including battery conditioning and charge suspended) 1 Hz flash
Fast charge (current regulation) Low
Top-off charge
Trickle maintenance charge (after fast charge)
Charge complete High impedance
Battery absent
Sleep mode
Sleep Mode
The bq24401 features a sleep mode for low power consumption. This mode is enabled when the voltage at the
BAT pin is above the low-power-mode threshold, V
SLP
. During sleep mode, the bq24401 shuts down all
unnecessary internal circuits, drives the LED output to high-impedance state, and drives the MOD pin low.
Restoring BAT below the V
MCV
threshold initiates the IC and starts a fast-charge cycle. Normally, the bq24401
only enters sleep mode when there is no battery connected on the output and the charger is idling with nothing to
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