BQ24298_15 Datasheet, PDF (23/51 Pages) Texas Instruments – bq24298 I2C Controlled 3A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

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bq24298
SLUSC59 – APRIL 2015
8.3.3.5 Charging Safety Timer
The device has safety timer to prevent extended charging cycle due to abnormal battery conditions. The safety
timer is 4 hours when the battery is below batlowv threshold. The user can program fast charge safety timer
(default 12 hours) through I²C (REG05[2:1]). When safety timer expires, the fault register REG09[5:4] goes 11
and an INT is asserted to the host. The safety timer feature can be disabled via I²C (REG05[3]).
The following actions restart the safety timer after safety timer expires:
• Toggle the CE pin HIGH to LOW to HIGH (charge enable)
• Write REG01[5:4] from 00 to 01 (charge enable)
• Write REG05[3] from 0 to 1 (safety timer enable)
During input voltage/current regulation, thermal regulation, or FORCE_20PCT bit (REG02[0]) is set , the safety
timer counting at half clock rate since the actual charge current is likely to be below the register setting. For
example, if the charger is in input current regulation (IINDPM) throughout the whole charging cycle, and the
safety time is set to 5 hours, the safety timer will expire in 10 hours. This feature can be disabled by writing 0 to
REG07[6].
8.3.3.5.1 Safety Timer Configuration Change
When safety timer value needs to be changed, it is recommended that the timer is disabled first before new
configuration is written to REG05[2:1]. The safety timer can be disable by writing 1 to REG05[3]. This ensures
the safety timer restart counting after new value is configured.
8.3.3.6 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.
8.3.4 Status Outputs (PG, STAT, and INT)
8.3.4.1 Power Good Indicator (PG) (bq24298)
In bq24298,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)
8.3.4.2 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.
Table 5. STAT Pin State
CHARGING STATE
Charging in progress (including recharge)
Charging complete
Sleep mode, charge disable
STAT
LOW
HIGH
HIGH
8.3.4.3 Interrupt to Host (INT)
In some applications, the host does not always monitor the charger operation. The INT notifies the system on the
device operation. The following events will generate a 256-µs INT pulse.
1. USB/adapter source identified (through PSEL detection and OTG pin)
2. Good input source detected
– not in sleep
– VBUS below V_ACOV threshold
– current limit above I_BADSRC
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