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

1.1 What is Liquid Detection and Why is It Needed?

In a connected state, the VBUS supports up to 20V (SPR) or 48V (EPR), while the CC and VCONN pins reach approximately 5V. Even in an unattached.SNK or unattached.SRC state, a DRP source pulls the CC lines to a voltage between 3V and 5V. This creates a risk of corrosion on the connector pins, which eventually damage the USB interface and the wider system, see corrosive damage to a type-C port in Figure 1-1. To mitigate this, the USB Type-C® Specification (Revision 2.3) introduced a liquid detection mode. This standard requires the device to transition to a 0V state to prevent corrosion.
Corrosion on Type-C Port Figure 1-1 Corrosion on Type-C Port

In an attached.SNK or attached.SRC state, the VBUS pins support up to 20V for SPR and a maximum of 48V for EPR along with the CC and Vconn pin reaching up to approximately 5V. Even in an unattached.SNK or unattached.SRC state a source only or DRP USB Type-C connector pulls the CC lines up to 3V-5V. In these states if the connector pins are shorted, the VBUS voltage levels eventually cause corrosion within the connector, damaging the USB interface and possibly the system as well. Having the ability to prevent and reduce corrosion damage can increase the lifetime of the system.

TPS25751A, TPS25752A, and TPS26750A devices from Texas Instruments are able to support the liquid corrosion mitigation method as described in the USB Type-C Specification to determine if a short is present on the USB Type-C connector. This methodology measures the leakage voltage between pins to determine if there is a short using dedicated measurement pin(s). TPS25751A, TPS25752A, and TPS26750A implement this feature using minimal external circuitry. This feature is also customizable through the USBCPD Application Customization Tool.