Datasheet

BAT
PACK
DSG
CHG
REG1/REG2
ChangetoShutdown
WakeUp
AllCellVoltage>(V +
UV
DV )or
AllCellVoltage>V
andDetecting(PACK+) – V >0.1V
UVH
UV
BAT
ConnectaCharger
UVDetection
UVDetection
T0374-01
Overcurrent in Discharge (OCD) Detection
Short Circuit in Discharge (SCD) Detection
bq77PL900
www.ti.com ...................................................................................................................................................... SLUS844B – JUNE 2008 – REVISED JANUARY 2009
In Stand-Alone Mode
On detecting entry to undervoltage mode, the bq77PL900 moves to the shutdown power mode.
When a charger is attached, the bq77PL900 wakes up from shutdown mode. If cell voltages are lower than the
undervoltage condition, the DSG FET is turned OFF and XALERT driven low. During periods when a charger is
attached, the bq77PL900 never changes to shutdown mode.
When the undervoltage recovery condition is satisfied, the DSG FET turns ON and XLAERT is reset high.
Figure 15. UV and UV Recovery in Stand-Alone Mode
The overcurrent in discharge detection feature detects abnormal currents in the discharge direction via
measuring the voltage across the sense resistor (V
OCD
) and is used to protect the pass FETs, cells, and any
other inline components from abnormal discharge current conditions. The detection circuit also incorporates a
blanking delay period (t
OCD
) before turning OFF the pass FETs. Both V
OCD
and t
OCD
can be programmed in
internal EEPROM.
The short circuit in discharge detection feature detects severe discharge current via measuring the voltage
across the sense resistor (V
SCD
) and is used to protect the pass FETs, cells, and any other inline components
from severe current conditions. The detection circuit also incorporates a blanking delay period (t
SCD
) before
turning OFF the pass FETs. Both V
SCD
and t
SCD
can be programmed in the internal EEPROM.
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