BQ24085 Datasheet, PDF (23/34 Pages) Texas Instruments – 750 mA SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION

bq24085, bq24086
bq24087, bq24088
www.ti.com .................................................................................................................................................... SLUS784B – DECEMBER 2007 – REVISED MAY 2008
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
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) (22 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 20
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 20. bq24085/6/7/8 Short Circuit Behavior
See the application section for additional details on start-up operation with V_(BAT) < V_(SC).
STARTUP WITH DEEPLY DEPLETED BATTERY CONNECTED
The bq24085/6/7/8 charger furnishes the programmed charge current if a battery is detected. If no battery is
connected the bq24085/6/7/8 operates as follows:
• The output current is limited to 22 mA (typical), if the voltage at BAT pin is below the short circuit detection
threshold V_(SC), 1.8 V typical.
• The output current is regulated to the programmed pre-charge current if V_(SC) < V_(BAT) < V_(LOWV).
• The output current is regulated to the programmed fast charge current If V_(BAT) > V_(LOWV) AND voltage
regulation is not reached.
The output voltage collapses if no battery is present and the end equipment requires a bias current larger that
the available charge current.
Copyright © 2007–2008, Texas Instruments Incorporated
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