BQ24297 Datasheet, PDF (32/48 Pages) Texas Instruments – I2C Controlled 3A Single Cell USB Charger

bq24296
bq24297
SLUSBP6A – SEPTEMBER 2013 – REVISED OCTOBER 2013
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When the host changes watchdog timer configuration (REG05[5:4]), it is recommended to first disable watchdog
by writing 00 to REG05[5:4] and then change the watchdog to new timer values. This ensures the watchdog
timer is restarted after new value is written.
POR
watchdog timer expired
Reset registers
I2C interface enabled
Y
I2C Write?
N
Default Mode
Reset watchdog timer
Reset registers
Host Mode
Start watchdog timer
Host programs registers
Reset REG01
Y
bit[6]?
N
Y
N
I2C Write?
Y
Watchdog Timer
N
Expired?
Figure 33. Watchdog Timer Flow Chart
Plug in USB100mA Source with Good Battery
When the input source is detected as 100mA USB host, and the battery voltage is above batgood threshold
(V_BATGD), the charger device enters HIZ state to meet the battery charging spec requirement.
If the charger device is in host mode, it will stay in HIZ state even after the USB100mA source is removed, and
the adapter plugs in. During the HIZ state, REG00[7] is set HIGH and the system load is supplied from battery. It
is recommended that the processor host always checks if the charger IC is in HIZ state when it wakes up. The
host can write REG00[7] to 0 to exit HIZ state.
If the charger is in default mode, when the DC source is removed, the charger device will get out of HIZ state
automatically. When the input source plugs in again, the charger IC runs detection on the input source and
update the input current limit.
USB Timer when Charging from USB100mA Source
The total charging time in default mode from USB100mA source is limited by a 45-min max timer. At the end of
the timer, the device stops the converter and goes to HIZ.
Status Outputs (PG, STAT, and INT)
Power Good Indicator (PG) (bq24296)
In bq24296, PG goes LOW to indicate a good input source when:
1. VBUS above V_{BUS_UVLO}
2. VBUS above battery (not in sleep)
3. VBUS below V_ACOV threshold
4. VBUS above V_{BUS_MIN} when I_BADSRC current is applied (not a poor source)
Charging Status Indicator (STAT)
The device indicates charging state on the open drain STAT pin. The STAT pin can drive LED as the application
diagram shows.
32
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