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Original question:

[参考译文] TCA9539-Q1：TCA9539QPWRQ1如何处理中断信号？

TCA9539-Q1: TCA9539-Q1 P04 PIN driving capability degraded

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Prodigy 20 points
Part Number: TCA9539-Q1

Dear TI Support Team,

We are encountering an issue with the TCA9539QPWRQ1 in one of our mass production projects and would appreciate your technical assistance.

Issue Description:
We have identified a failure on Port 4 of the TCA9539QPWRQ1. The specific symptom is that the channel cannot drive a digital transistor (MPN: PDTC124ET-QR).

When we issue a command to set P04 high, the command is sent successfully (writing ‘1’), but the readback state remains ‘0’. All other ports are functioning normally; only Port 4 is affected.

Debugging Steps & Observations:

  • We removed the transistor and connected an external resistor from Port 4 to GND.

  • With a 50kΩ pull-down resistor, the measured voltage on the damaged board is 0.146V.

  • With a 100kΩ resistor, the voltage is 0.265V.

  • On a known-good board, the voltage at the same port is 3.299V under both conditions.

  • The current output from the damaged Port 4 is only 3.5μA.

We suspect Port 4 may be permanently damaged, and would like to understand:

  1. Possible failure mechanisms or known issues that could cause this behavior?

  2. Whether this could be due to overstress, or if similar failure patterns have been observed with this device?

  3. Any recommendations to improve robustness or further diagnostic methods?

  • 0
    TI__Mastermind 29185 points

    您好，

    已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

  • 0
    TI__Mastermind 36630 points

    1.For point 1, and given the debug setup, it seems that the pin is damaged. A 50k or 100k PD resistor should be a very small resistive load to drive HIGH. What I mean, is that the VOH should be near VCC under good case, since the pFET pulls the pin HIGH. 

    A reading that shows a voltage only 0.146V or 0.265V for various weak PD resistors shows that the pin is internally damaged and cannot pull HIGH. 

    The damage could have been from electrical overstress where too much current was sourced or sink from the pin. Each pin allows for +/-50mA abs. max for the current range. Anything above this could result in permanent damage to the device, often times, the internal pFET or nFET of the output structure is burned up. 

    Potential solder bridge could bridge two pins where the outputs are opposite. One output drives high another drives LOW creating a PWR to GND short. 

    ESD could also play a role in damaging the output pin. Not sure the ESD environment for this project. 

    2. I have seen this in other customer's designs but it is usually due to overstressing the pin by sourcing / sinking too much current in/out of the pin when the pin is configured as an output HIGH/LOW. 

    3.Add series resistance on the pin to limit over-current events.

    Add external ESD protection diodes to protect against larger ESD artifacts. 

    Have a solder check to ensure that no two pins short together via solder bridge.