BQ24765_15 Datasheet, PDF (28/37 Pages) Texas Instruments – SMBus-Controlled Multi-Chemistry Battery Charger With Integrated Power MOSFETs

bq24765
SLUS999 – NOVEMBER 2009
ACIN
ACOK
Comparator
-
2.4V +
ACOK
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ACOK_DG
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ACOK
CSSP
CSSN
VICM
Current Sense
1k
Amplifier
+
-
ICREF
VICM
Error
20k
Amplifier
Disable
-
+
Program Hysteresis of
comparator
by putting a resistor in feedback
from ICOUT pin to ICREF pin.
VICM
Disable
Input Current
Comparator
+
-
VICM
ICOUT
Figure 31. ACOK, ICREF, and ICOUT Logic
OPEN-DRAIN STATUS OUTPUTS (ACOK, ICOUT PINS)
Two status outputs are available, and they both require external pull up resistors to pull the pins to system digital
rail for a high level. ACOK open-drain output goes high when ACIN is above 2.4V. It indicates a good adapter is
connected because of valid input voltage. ICOUT open-drain output goes low when the input current is higher
than the programmed threshold via ICREF pin. Hysteresis can be programmed by putting a resistor from ICREF
pin to ICOUT pin.
THERMAL SHUTDOWN PROTECTION
The QFN package has low thermal impedance, which provides good thermal conduction from the silicon to the
ambient, to keep junctions temperatures low. As added level of protection, the charger converter turns off and
self-protects whenever the junction temperature exceeds the TSHUT threshold of 155°C. VDDP LDO is disabled
as well during thermal shut down. The charger stays off until the junction temperature falls below 135°C. Once
the temperature drops below 135°C, VDDP LDO is enabled. If all the conditions described in “Enable and
Disable Charging” section are valid, charge will soft start again.
CHARGER TIMEOUT
The bq24765 includes a timer to terminate charging if the charger does not receive a ChargeVoltage() or
ChargeCurrent() command within 170s. If a timeout occurs, both ChargeVoltage() and ChargeCurrent()
commands must be resent to re-enable charging.
CHARGE TERMINATION FOR LI-ION OR LI-POLYMER
The primary termination method for Li-Ion and Li-Polymer is minimum current. Secondary temperature
termination (see Charge Current Regulation section) also provides additional safety. The host controls the charge
initiation and the termination. A battery pack gas gauge assists the hosts on setting the voltages and determining
when to terminate based on the battery pack state of charge.
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