BQ24704 Datasheet, PDF (20/31 Pages) Texas Instruments – Low Cost, Host-Controlled Li-Ion and Li-Polymer Battery Charger With Low Iq

bq24704
SLUS838 – MAY 2009........................................................................................................................................................................................................ www.ti.com
BATTERY OVERVOLTAGE PROTECTION
The converter stops switching when BAT voltage goes above 104% of the regulation voltage. The converter will
not allow the high-side FET to turn on until the BAT voltage goes below 102% of the regulation voltage. This
allows one-cycle response to an overvoltage condition, such as when the load is removed or the battery is
disconnected. A 10-mA current sink from BAT to PGND is on only during charge, and allows discharging the
stored output-inductor energy into the output capacitors.
CHARGE OVERCURRENT PROTECTION
The charger has a secondary overcurrent protection. It monitors the charge current, and prevents the current
from exceeding 145% of regulated charge current. The high-side gate drive turns off when the overcurrent is
detected, and automatically resumes when the current falls below the overcurrent threshold.
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. The charger stays off
until the junction temperature falls below 135°C.
Status Outputs (ACGOOD, DPMDET)
Two status outputs are available, and they require external pull up resistors to pull the pins to system digital rail
for a high level.
ACGOOD open-drain output goes low if ACDET is above 2.4 V.
DPMDET open-drain output goes low when the DPM loop is active to reduce the battery charge current (after a
10-ms delay).
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