SDAA491 October   2026 TPS25751A , TPS25752A , TPS26750A

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 What is Liquid Detection and Why is It Needed?
    2. 1.2 Definitions
    3. 1.3 Liquid Detection Method Overview
  5. 2Detailed Description
    1. 2.1 Hardware Implementation and Requirements
      1. 2.1.1 GPIO Hardware Requirements
    2. 2.2 Firmware Implementation and Requirements
      1. 2.2.1 Interrupt Event/Mask/Clear for I2C1 (register 0x14/0x16/0x18)
      2. 2.2.2 GPIO Configuration (register 0x5c)
      3. 2.2.3 Liquid Detection Configuration (register 0x98)
        1. 2.2.3.1 Wait Timing
          1. 2.2.3.1.1 Wait Time in Seconds Non-Liquid [7:0]
          2. 2.2.3.1.2 Wait Time in Seconds Liquid [15:8]
        2. 2.2.3.2 Sample Timing and Retires
          1. 2.2.3.2.1 Sample Time in 10ms No Liquid [19:16]
          2. 2.2.3.2.2 Sample Time in 10ms Liquid [23:20]
          3. 2.2.3.2.3 Liquid Detection Retries Wait Time [27:24]
          4. 2.2.3.2.4 Liquid Detection Retries [31:28]
          5. 2.2.3.2.5 Number of Samples [39:32]
        3. 2.2.3.3 High and Low Threshold Measurements
          1. 2.2.3.3.1 Low Threshold ADC No Liquid [47:40]
          2. 2.2.3.3.2 High Threshold ADC No Liquid [55:48]
          3. 2.2.3.3.3 Low Threshold ADC Liquid [63:56]
          4. 2.2.3.3.4 High Threshold ADC Liquid [71:64]
        4. 2.2.3.4 Enable Liquid Detection [72]
        5. 2.2.3.5 Enable Corrosion Mitigation [73]
        6. 2.2.3.6 Monitor During Attach [74]
        7. 2.2.3.7 Monitor During Unattached [75]
        8. 2.2.3.8 Liquid Pins to Monitor [77:76]
        9. 2.2.3.9 Pulldown Threshold ADC [87:88]
  6. 3Detailed Application Procedure
    1. 3.1 Example Liquid Detection Configuration
    2. 3.2 Application Performance Plots
      1. 3.2.1 Number of Samples Waveform
      2. 3.2.2 Sample Time in No Liquid Waveform
      3. 3.2.3 Sample Time in Liquid Waveform
      4. 3.2.4 Wait Time in No Liquid Waveform
      5. 3.2.5 Wait Time in Liquid Waveform
      6. 3.2.6 Entering Liquid Detection Waveform
      7. 3.2.7 Exiting Liquid Detection Waveform
      8. 3.2.8 Corrosion Mitigation Disabled Waveform
  7. 4Summary
  8. 5References

1.2 Definitions

This section identifies keywords and definitions within this document. Definitions are based on the USB Power Delivery Specification Revision 3.2.

    Corrosion Mitigation Reduces corrosion risk by driving the CC pins to a near-zero voltage level, preventing unintended current flow during unattached states.
    Attached state The device has detected a valid connection through the CC pin(s) — meaning a cable and/or partner device is plugged in, and the correct pull-up (Rp) / pull-down (Rd) termination has been sensed for a minimum debounce time (tCCDebounce). Once attached, the port locks in its role (source or sink) and moves into states such as Attached.SRC or Attached.SNK.
    Unattached state In this state, a port is actively driving/monitoring its CC pin(s) to detect a potential connection. There are typically sub-states like Unattached.SNK and Unattached.SRC, where the port alternates checking whether it should behave as a source or sink, based on pull-up/pull-down resistor detection on CC.
    Entering Liquid Detected state The port detects electrical behavior on monitoring pins consistent with liquid or contamination, so it assumes water/corrosive material is present.

    Upon entering this state the port is classified as wet.
    Exiting Liquid Detected state

    The port detects the monitoring pins surpass the dry thresholds— for example, the monitoring pins return to values consistent with the no liquid conditions (indicating the liquid has dried or drained).

    Upon entering this state the port is classified as dry.