7.4 Overtemperature Protection (OTP) and De-Rating
The host MCU can access the estimated temperature of a potential hot spot by accessing the TEMP register. A NTC thermistor is used to
connect to the OTP pin and ground nearby the potential hot spot. The host MCU must initialize the TR25, TR50, TR75, and TR100 registers
before reading the TEMP register or enabling OTP and power de-rating functions.
The default value of the OTPTHR register is 78h (120°C), which can be updated through the I2C interface. If the TEMP value rises over the
OTPTHR value after the de-bouncing time (30ms), the STATUS.OTP will be set to 1 and the associated VOUT MOS switches are turned off.
The host MCU will need to load a new PD_CMDMSG to start the PD negotiation process, resuming quick-charging operation.
Furthermore, the AP33772S defines the DRTHR register as the threshold temperature value to trigger the power de-rating functions. If the
requested source PDO is PPS APDO, and when the TEMP value rises over the DRTHR value after de-bouncing time (30ms), the input current
will be reduced by 50% through sending out a new RDO to negotiate with the PD source device.
The AP33772S continuously monitors the temperature at the potential hot spot. After a time duration, if the TEMP value under the DRTHR value
is more than 10°C, the device will recover charging power.
7.5 Moisture Detection
After connecting to the Power Source, the AP33772S will first check whether the impedance of the DN pin is abnormal. If the DN impedance
check fails, the AP33772S goes into the MOISTURE state and does not acknowledge the Source Capability Messages.
In the MOISTURE state, the associated VOUT MOS switches are turned off with the LED flickering in the “MOISTURE” pattern. The AP33772S
will check the DN impedance over 2200ms. If the DN pin impedance check is normal, the AP33772S will start to negotiate with the source.
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