BQ24745_14 Datasheet, PDF (27/39 Pages) Texas Instruments – SMBus-Controlled Multi-Chemistry Battery

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ACIN
ACOK
Comparator
-
2.4V +
ACOK
bq24745
SLUS761D – DECEMBER 2007 – REVISED OCTOBER 2011
ACOK
CSSP
CSSN
ICREF
VICM
1k
Current Sense
Amplifier
+
-
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 36. ACOK, ICREF, and ICOUT Logic
OPEN-DRAIN STATUS OUTPUTS (ACOK, ICOUT PINS)
Two status outputs are available; both require external pullup resistors to pull the pins to the system digital rail for
a high level.
The ACOK open-drain output goes high when ACIN is above 2.4 V. It indicates that a functional adapter is
providing a valid input voltage.
The ICOUT open-drain output goes low when the input current is higher than the threshold programmed via the
ICREF pin. Hysteresis can be programmed by adding a resistor from the ICREF pin to the 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 the junction temperature low. As an 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 shutdown. The charger stays off until the junction temperature falls below 135°C.
Once the temperature drops below 135°C, the VDDP LDO is enabled. If all the conditions described in the
Enable and Disable Charging section are valid, charge soft-starts again.
CHARGER TIME-OUT
The bq24745 includes a timer to terminate charging if the charger does not receive a ChargeVoltage() or
ChargeCurrent() command within 170 s. If a time-out 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 the 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.
Copyright © 2007–2011, Texas Instruments Incorporated
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