BQ24292I Datasheet, PDF (30/42 Pages) Texas Instruments – I2C Controlled 4.5A Single Cell USB/Adapter Charger With Narrow VDC Power Path Management and USB OTG

bq24292i
SLUSBI4 – APRIL 2013
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Thermal Regulation and Thermal Shutdown
The charger 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 charger device closely monitors the input and system voltage, as well as HSFET and LSFET current for safe
buck mode operation.
Input Over-Voltage (ACOV)
The maximum input voltage for buck mode operation is 18V. If VBUS voltage exceeds 18V, the device stops
switching immediately. During input over voltage (ACOV), the fault register REG09[5:4] will be set to 01. An INT
is asserted to the host.
System Over-Voltage Protection (SYSOVP)
The charger device monitors the voltage at SYS. When system over-voltage is detected, the converter is stopped
to protect components connected to SYS from high voltage damage.
Over-Current Protection in Boost Mode
The charger device closely monitors the Q1, Q2(HSFET) and Q3(LSFET) current to ensure safe boost mode
operation. During over-current condition, the device will operate in hiccup mode for protection. While in hiccup
mode cycle, the device turns off Q1 FET for t_{OTG_OCP_OFF} (32ms typical) and turns on Q1 FET for
t_{OTG_OCP_ON}(100us typical) in an attempt to restart. If the over-current condition is removed, the boost converter
will maintain the Q1 FET on state and the VBUS OTG output will operate normally. When over-current condition
continues to exist, the device will repeat the hiccup cycle until over-current condition is removed.
VBUS Over-Voltage Protection in Boost Mode
The boost mode regulated output is 5V. When an adapter plugs in during boost mode, the VBUS voltage will rise
above regulation target. Once the VBUS voltage exceeds V_{OTG_OVP}, the charger device stops switching and the
device exits boost mode. The fault register REG09[6] is set high to indicate fault in boost operation. An INT is
asserted to the host.
Battery Protection
Battery Over-Current Protection (BATOVP)
The battery over-voltage limit is clamped at 4% above the battery regulation voltage. When battery over voltage
occurs, the charger device immediately disables charge. The fault register REG09[5] goes high and an INT is
asserted to the host.
Charging During Battery Short Protection
If the battery voltage falls below 2V, the charge current is reduced to 100mA for battery safety.
System Over-Current Protection
If the system is shorted or exceeds the over-current limit, the BATFET is latched off. DC source insertion on
VBUS is required to reset the latch-off condition and turn on BATFET.
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