BQ24085_17 Datasheet, PDF (21/42 Pages) Texas Instruments – 750-mA Single-Chip Li-Ion and Li-Pol Charge Management IC With Thermal Regulation

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bq24085, bq24086, bq24087, bq24088
SLUS784E – DECEMBER 2007 – REVISED DECEMBER 2015
bq24085/6/7/8
STANDBY
CHARGING
SUSPEND
SUSPEND
CHARGING, TMR PIN NOT OPEN
CHARGING, TMR PIN OPEN
Table 7. Charge Safety Timer Operational Modes
V(OUT) > V_(LOWV)
X
No
No
Yes
Yes
X
CHARGE SAFETY TIMER MODE
RESET
RESET
RESET
SUSPEND
COUNTING
RESET
In SUSPEND mode, the charge safety timer is put on hold (that is, charge safety timer is not reset), normal
operation resumes when the TS fault is removed and the timer returns to the normal operating mode
(COUNTING). If charge termination is not reached within the timer period, a fault condition is detected. Under
those circumstances, the LED status is updated to indicate a fault condition and the charger is turned off.
When the charge safety timer fault latch is set and the charger is turned off, a small current IFAULT is applied to
the OUT pin, as long as input power (IN) is detected AND V_(OUT) < V_(RCHG), as part of a timer fault recovery
protocol. This current allows the output voltage to rise above the recharge threshold V_(RCHG) if the pack is
removed, and assures that the charge safety timer fault latch is reset if the pack is removed and re-inserted.
Table 8 further details the charge safety timer fault latch operation.
Table 8. Charge Safety Timer Latch Functionality
CHARGE SAFETY TIMER FAULT ENTERED
V_(OUT) > V_{(LOW V)}
CHARGE SAFETY TIMER FAULT LATCH RESET AT
CE rising edge, or OVP detected
Input power removed (not detected)
New charging cycle started; see state diagram
8.3.15 Short-Circuit Protection
The internal comparators monitor the battery voltage and detect when a short circuit is applied to the battery
terminal. If the voltage at the BAT pin is less than the internal threshold V_(SCIND) (1.8 V typical), the STAT pins
indicate a fault condition (STAT1 = STAT2 = Hi-Z). When the voltage at the BAT pin falls below a second internal
threshold V_(SC) (1.4 V typical), the charger power stage is turned off. A recovery current, I_(SHORT) (15 mA typical),
is applied to the BAT pin, enabling detection of the short circuit removal. The battery output current versus
battery voltage is shown in the graph, Figure 16.
1200
R_ISET at 840 W
1000
800
600
400
200
0
4 3.5 3 2.5 2 1.5 1 0.5 0
Battery Voltage - V
Figure 16. bq24085/6/7/8 Short Circuit Behavior
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