bq29330
www.ti.com
SLUS673A–SEPTEMBER 2005–REVISED DECEMBER 2005
FUNCTIONAL DESCRIPTION (continued)
WDRST = L
REG Output
Normal Operation
RST Output
t
WDTINT (500 ms)
t
WDWT
t
RST
WDI Input
XALERT
CHG, DSG, and
ZVCHG = OFF
FET Control
Access by Host
WDRST = H
REG Output
RST Output
Normal Operation
Twice
t
WDTINT (500 ms)
t
WDWT
t
t
t
RST
RST
RST
t
WDTINT (500 ms)
WDI Input
XALERT
CHG, DSG, and
ZVCHG = OFF
FET Control
Access by Host
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 VBAT 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
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