BQ24721 Datasheet, PDF (38/48 Pages) Texas Instruments – ADVANCED MULTI-CHEMISTRY AND MULTI-CELL SYNCHRONOUS SWITCH-MODE CHARGER AND SYSTEM POWER SELECTOR

bq24721
SLUS683 – NOVEMBER 2005
www.ti.com
BIT
SBS SPEC
bq24721 SBS-Like
BATTERY CONNECTED TO SYSTEM (by selector BATDRV)
(Note: Added Feature, Not part of SBS spec.)
HI indicates the battery is connected to the system output. LO indicates battery is not connected.
During this HI state, the BATDRV pin is pulled 6V below the SYS pin voltage to turn on the external
PMOS BAT FET. When in LO state, the BATDRV pin voltage is pulled-up to the SYS pin voltage.
6
CURRENT_OR
Battery is connected to system when ac is not present, or when ac is present and LEARN CYCLE is
set at the control register.
FEATURE: If in learn cycle and the battery falls below the BATDEP threshold (programmed by the
control register), then the IC automatically switches from battery power to ac adapter power.
FEATURE: Also, in all cases if system (SYS) voltage is more than 150 mV above the battery (BAT)
voltage then the BAT FET is kept off until SYS discharges to within 150 mV to prevent the system
capacitors from discharging into the battery. This feature protects the battery from extended high surge
currents.
ADAPTER CONNECTED TO SYSTEM (by selector ACDRV)
(Note: Added Feature, Not part of SBS spec.)
HI indicates the adapter is connected to the system output. LO indicates adapter is not connected.
During this HI state, the ACDRV pin is pulled 6 V below the PVCC pin voltage to turn on the external
PMOS AC FET. When in LO state, the ACDRV pin voltage is pulled-up to the PVCC pin voltage.
7
VOLTAGE_OR
AC is connected to system when adapter is present (ACDET voltage is above threshold) and LEARN
CYCLE is not set at the control register.
FEATURE: If in learn cycle and the battery falls below the BATDEP threshold (programmed by the
control register), then the IC automatically switches from battery power to ac adapter power.
FEATURE: If there is an adapter overcurrent (ACOC) is detected, then the AC FET is turned off
immediately to prevent a short-circuit condition or a surge current. This feature protects the battery
from extended high surge currents.
IC THERMAL SHUTDOWN FAULT
(Note: Added Feature, Not part of SBS spec.)
A HI indicates the IC temperature is too high, and had to turn-off the charger. LO indicates temperature
is safe.
8
THERMISTOR_OR
FAULT DETECTION AND PROTECTION FEATURE: The IC monitors its own junction temperature. If
the IC junction temperature exceeds 145°C, then the IC automatically shuts down the charger and an
ALARM is triggered. SMBus communications continues to function. The charger remains off until the IC
junction temperature falls below 130°C. The charger automatically restarts once the temperature falls
below the hysteresis at 130°C.
[THERMISTOR COLD
HI indicates the thermistor temperature is too cold to allow charging. The TS pin voltage threshold
9
THERMISTOR_COLD
would be higher than the TS cold voltage threshold when this bit is HI. A LO means the TS voltage is
below the TS cold voltage threshold. Programmed by a voltage divider pulled up to the VREF5 pin.
Note: VREF5 only comes up when ac is detected to conserve battery power, since no charging would
be required.
THERMISTOR HOT (start) or (operating)
HI indicates the thermistor temperature is too hot to allow charging. The TS pin voltage threshold would
be lower than the TS hot voltage threshold when this bit is HI. A LO means the TS voltage is above the
10 THERMISTOR_HOT TS hot voltage threshold. There is a different voltage threshold before starting charge than during
charging (operating). Programmed by a voltage divider pulled up to the VREF5 pin.
Note: VREF5 only comes up when AC is detected to conserve battery power, since no charging would
be required.
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