BQ24188_15 Datasheet, PDF (21/52 Pages) Texas Instruments – bq24188 2A, 30V, Host-Controlled Single-Input, Single Cell Switchmode Li-Ion Battery Charger with Power Path Management and USB-OTG Support

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bq24188
SLUSC44A – DECEMBER 2014 – REVISED MAY 2015
Device Functional Modes (continued)
In addition to the safety timer, the bq24188 contains a 30-second (t_WATCHDOG) watchdog timer that monitors the
host through the I²C interface. Once a write is performed on the I²C interface, a watchdog timer is started. The
watchdog timer is reset by the host using the I²C interface. This is done by writing a “1” to the reset bit
(TMR_RST) in the control register. The TMR_RST bit is automatically set to “0” when the watchdog timer is
reset. This process must continue as long as the input is connected in order to maintain the register contents. If
the watchdog timer expires, the IC enters DEFAULT mode where the default register values are loaded, the
safety timer restarts at 2 minutes once charging continues. The I²C may be accessed again to reinitialize the
desired values and restart the watchdog timer. The watchdog timer flow chart is shown in Figure 12.
Start Safety Timer
Safety timer expired? ^Yes
No
Charge Done?
I_CHG < I_TERM
No
Yes ^{STAT = Hi}
Update STAT
bits
No
I²C Write
performed?
Yes
Start watchdog timer
Safety timer
fault
Charging suspended
Enter suspended
mode
Fault indicated in
STAT registers
Charge Done? ^Yes
I_CHG < I_TERM
STAT = Hi
Update STAT
bits
Reset watchdog timer
No
Yes
Safety timer expired?
Safety timer
fault
No
WD timer expired?
Yes
Charging suspended
Enter suspended
mode
Fault indicated in
STAT registers
No
Yes
No
Received
software watchdog
RESET?
Reset to default
values in I²C
register
Restart 2 min
safety timer
Figure 12. The Watchdog Timer Flow Chart for bq24188
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