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TPS25751: Moisture detection behavior in detail

Chao Fu Chen
Intellectual 1170 points
Part Number: TPS25751

Hi Expert,

Please help to comment question as bleow;

  1. Description of the operating principle of the liquid detection circuit
  2. Experimental data proves that this method is effective
  3. What are the risks of using the SBU pin for detection instead of using the CC pin for detection? Why does there not be such a risk when using the SBU pin?
  4. When TPS25751 is used in a power adapter, how to use the CC pin and how to connect the circuit? Since the switch is changed from SBU to CC pin, what are the risks when connecting in this way?

Eddie

  • 0
    TI__Mastermind 34466 points

    Hi Eddie, 

    Chao Fu Chen said:
    Description of the operating principle of the liquid detection circuit

    The liquid detection on TPS25751 utilizes the ADCIN pins (GPIO4 and GPIO5) to measure the voltage reading on the SBU pins of the Type-C connector/port. The FETs (PFET and NFET) toggles the Liquid Detection lines to either pull-up to 3.3V or pull-down to GND to measure any abnormal voltage reading. During a dry-state (no liquid on the Type-C Connector), the high reading should be close to 3.3V and the low reading should be close to GND level. If liquid is present on the Type-C Connector (shorting SBU to VBUS/CC or SBU to GND), this will change the normal reading on the Liquid Detection lines resulting in the PD entering a Liquid Detected state. 

    Chao Fu Chen said:
    Experimental data proves that this method is effective

    Refer to page 56 on the TPS25751 datasheet: https://www.ti.com/lit/ds/symlink/tps25751.pdf?ts=1702315777251&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPS25751 

    Chao Fu Chen said:
    What are the risks of using the SBU pin for detection instead of using the CC pin for detection? Why does there not be such a risk when using the SBU pin?

    The CC pins are already used for PD communication. Since the SBU pins are not used for TPS25751 (does not support Alternate Modes such as DP, TBT, etc.) they are no serial communication concerns for interference(s). 

    Chao Fu Chen said:
    When TPS25751 is used in a power adapter, how to use the CC pin and how to connect the circuit? Since the switch is changed from SBU to CC pin, what are the risks when connecting in this way?

    Not sure what the ask is here, are you asking if the CC lines can be connected to the liquid detection circuit instead of the SBU pins? TPS25751 Liquid Detection is set up to utilize the SBU pins, any other pins from the Type-C Connector is not supported. 

    Do keep in mind TPS25751 is currently in preview and we are validating certain functions (including liquid detection) for RTM (scheduled for 2Q24). 

    Thanks and Regards,

    Raymond Lin