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PCF8574 Temperature Sensitivity

Samuel Jaffe
Mastermind 25590 points
Other Parts Discussed in Thread: PCF8574

Hi E2E,

My customer is seeing failures in their system at 70C.  The failure seems to get fixed when they replace the PCF8574.  Our questions are:

  • Are there any internal protections to cause thermal shut down? And what thresholds would they have?
  • Are we aware of any issues at higher temperatures?
  • Might the I2C bus be susceptible to issues at higher temperatures?
  • The recommended ‘operating free-air temperature’ is from -40 °C to 85 °C. Does TI test all production parts to 85 °C? And how high of temperature did qualification testing get to?

Edit: A few more questions:

  • Does Figure 11 of the datasheet (picture below) correspond to the P port or the I2C port?
  • With all 8 ports configured as inputs, they expect to be pulling about 0.25mW when accessing the I2C ports.  Does this sound reasonable?

Thank you,

-Sam

  • 0
    TI__Mastermind 23116 points
    Hello Sam,
    Sorry for the delay in response.
    Generally thermal shutdowns are set 5-10C above the abs max junction temp. Our parts are characterized over the max operating temp so they should be fine assuming you keep the part's max junction temperature within the specified range.

    Have you measured the case temp of the part to make sure that the part isn't getting to hot, either by load on IOs or due to localized heating from other devices? You need to make sure the part isn't seeing temps outside its specifications.

    Figure 11 does refer to P port.

    What is on the input ports? Is it pulled high or low?
    -Francis Houde
  • 0 in reply to fhoude
    TI__Mastermind 25590 points
    Francis,

    It looks like the issue was due to heating. IC temp was above rated. Thanks for the support!

    -Sam
  • 0 in reply to Samuel Jaffe
    TI__Mastermind 23116 points
    Hello Same,
    Thanks for getting back to us and verifying what the problem was! Hopefully this thread will help other E2E users in the future.
    Sincerely,
    -Francis Houde