BQ29330 Datasheet, PDF (16/26 Pages) Texas Instruments – 2-,3-,AND 4-CELL LITHIUM-ION OR LITHIUM-POLYMER BATTERY PROTECTION AFE

bq29330
SLUS673A – SEPTEMBER 2005 – REVISED DECEMBER 2005
FUNCTIONAL DESCRIPTION (continued)
WDRST = L
REG Output
RST Output
WDI Input
Normal Operation
t_RST
t_WDWT
t_{WDTINT (500 ms)}
XALERT
FET Control
Access by Host
CHG, DSG, and
ZVCHG = OFF
WDRST = H
REG Output
RST Output
WDI Input
Normal Operation
t_RST
t_WDWT
Twice
t_{WDTINT (500 ms)}
t_RST
t_RST
t_{WDTINT (500 ms)}
XALERT
FET Control
Access by Host
CHG, DSG, and
ZVCHG = OFF
www.ti.com
Figure 4. Watchdog Timing Chart – WDI Fault After Startup
DSG and CHG NCH FET DRIVER CONTROL
The bq29330 drives either the DSG or CHG FET off if an OL, SCC, or SCD safety threshold is breached
depending on the current direction. The host can force any FET on or off only if the bq29330 integrated
protection control allows.
The default-state of the FET drive is off. A host can control the FET drive by programming OUTPUT_CONTROL
(b2...b0), where b0 is used to control the discharge FET, b1 is used to control the charge FET, and b2 is used to
control the ZVCHG FET. These controls are only valid when not in the initialized state. The CHG drive FET can
be powered by PACK and the DSG FET can be powered by BAT.
When the bq29330 powers down, the NCH FET drivers power down to GND causing the FETs to turn off.
PRECHARGE AND 0 V CHARGING
The bq29330 supports both a charger that has a precharge mode and one that does not. The bq29330 also
supports charging even when the battery falls to 0 V. In order to charge, the charge FET (CHG) must be turned
on to create a current path. When the V_BAT is ~0 V, the V_(PACK) is as low as the battery voltage. In this case, the
supply voltage for the device is too low to operate.
16