Datasheet

Start Safety Timer
No
I C Read/Write
performed?
2
No
Yes
No
Yes
Received SW watchdog
RESET?
No
Yes
Safety timer expired?
No
Yes
Safety timer
fault
Charging suspended
Enter suspended
mode
Fault indicated in
STAT registers
Yes
Charge Done?
I
CHG
< I
TERM
No
STAT = Hi
Update STAT
bits
Yes
Reset 30 second
watchdog timer
Reset to default
values in I C
register.
Restart 27 min
safety timer
2
Charging suspended
Fault indicated in
STAT registers
No
Yes
STAT = Hi
Update STAT
bits
Start 30 second
watchdog timer
Charge Done?
I
CHG
< I
TERM
Safety timer
fault
Safety timer expired?
30 timer expired?
bq24272
SLUSB09 –JUNE 2012 www.ti.com
Figure 4. The Watchdog Timer Flow Chart for bq24272
Hardware Chip Disable Input (CD)
The bq24272 contain a CD input pin that is used to disable the IC and place the bq24272 into high-impedance
mode. Drive CD low to enable charge and enter normal operation. Drive CD high to disable charge and place the
bq24272 into high-impedance mode. Driving CD high during DEFAULT mode resets the safety timer. Driving CD
high during HOST mode resets the safety timer.
LDO Output (DRV)
The bq24272 contains a linear regulator (DRV) that is used to supply the internal MOSFET drivers and other
circuitry. Additionally, DRV supplies up to 10mA external loads to power the STAT LED or the USB transceiver
circuitry. The maximum value of the DRV output is 5.45V so it ideal for protecting voltage sensitive USB circuits
from high voltage fluctuations in the supply. The LDO is on whenever a supply is connected to the IN input of the
bq24272. The DRV is disabled under the following conditions:
1. V
IN
< UVLO
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