BQ24295 Datasheet, PDF (32/45 Pages) Texas Instruments – I2C Controlled 3A Single Cell USB Charger

bq24295
SLUSBC1 – SEPTEMBER 2013
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2. Good input source detected
– not in sleep
– VBUS below V_ACOV threshold
– current limit above I_BADSRC
3. Input removed or VBUS above V_ACOV threshold
4. Charge Complete
5. Any FAULT event in REG09
For the first four events, INT pulse is always generated. For the last event, when a fault occurs, the charger
device sends out INT and latches the fault state in REG09 until the host reads the fault register. If a prior fault
exists, the charger device would not send any INT upon new faults except NTC fault (REG09[2:0]). The NTC
fault is not latched and always reports the current thermistor conditions. In order to read the current fault status,
the host has to read REG09 two times consecutively. In order to read the current fault status, the host has to
read REG09 two times consecutively. The 1^st reads fault register status from the last read and the 2^nd reads the
current fault register status.
Protections
Input Current Limit on ILIM
For safe operation, the device has an additional hardware pin on ILIM to limit maximum input current on ILIM pin.
The input maximum current is set by a resistor from ILIM pin to ground as:
I_INMAX
=
1V
R_ILIM
´ K_LIM
(2)
The actual input current limit is the lower value between ILIM setting and register setting (REG00[2:0]). For
example, if the register setting is 111 for 3A, and ILIM has a 316Ω resistor to ground for 1.5A, the input current
limit is 1.5A. ILIM pin can be used to set the input current limit rather than the register settings.
The device regulates ILIM pin at 1V. If ILIM voltage exceeds 1V, the device enters input current regulation (Refer
to Dynamic Power Path Management section).
The voltage on ILIM pin is proportional to the input current. ILIM pin can be used to monitor the input current
following Equation 3:
IIN
=
V_ILIM
1V
´ I_INMAX
(3)
For example, if ILIM pin sets 2A, and the ILIM voltage is 0.75V, the actual input current 1.5A. If ILIM pin is open,
the input current is limited to zero since ILIM voltage floats above 1V. If ILIM pin is short, the input current limit is
set by the register.
Thermal Regulation and Thermal Shutdown
During charge operation, the device monitors the internal junction temperature T_J to avoid overheat the chip and
limits the IC surface temperature. When the internal junction temperature exceeds the preset limit (REG06[1:0]),
the device lowers down the charge current. The wide thermal regulation range from 60°C to 120°C allows the
user to optimize the system thermal performance.
During thermal regulation, the actual charging current is usually below the programmed battery charging current.
Therefore, termination is disabled, the safety timer runs at half the clock rate, and the status register REG08[1]
goes high.
Additionally, the device has thermal shutdown to turn off the converter. The fault register REG09[5:4] is 10 and
an INT is asserted to the host.
Voltage and Current Monitoring in Buck Mode
The device closely monitors the input and system voltage, as well as HSFET and LSFET current for safe buck
mode operation.
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