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SN74LVC1G175: Need some constants to calculate MTBF

Darren (FAE)
Expert 5483 points
Part Number: SN74LVC1G175

This app note describes the process of calculating MTBF, for when D changes state within the setup/hold timing window of the CLK edge; which creates a metastable condition.

From the app note, it shows calculations will be considerably easier if τ and t0 data is already characterized...this data doesn't have to be precise, but is it available somewhere for the LVC logic series? Specifically any data on these values for SN74LVC1G175DCKR? 

The data doesn't have to be "official"; just a guideline to get a rough idea if MTBF will be several minutes or several hundred years, etc for a given application.

Regards,
Darren

  • 0
    TI__Guru* 96591 points

    Hi Darren,

    There's a physical failure MTBF listed on the quality page for the device: https://www.ti.com/quality/docs/estimator.tsp

    For the SN74LVC1G175 the MTBF is listed as 2.14 x 10^9 hours.

  • 0 in reply to Emrys Maier
    TI__Expert 5483 points

    Hi Emrys,

    I appreciate the quality page link, but I already visited the page...:(
    The qualification doesn't list the CLK and D signal frequencies during the test though, right?

    These values seem pretty important, as a failure for the D-type Flip Flop occurs when there is a metastable state; aka the D input has a transition within the setup/hold time around the CLK input signal edge.

    From the above literature I attached, it looks like I should be able to calculate τ and t0 given the MTBF time from the quality page, as long as I know what the frequencies were during the test.

    MTBF is highly dependent upon these clocks.

    Can you see if that information is available? If so you could send it to me offline (I am in the Directory Services)?

    Thanks,

    Darren

  • 0 in reply to Darren (FAE)
    TI__Guru* 96591 points

    Hey Darren,

    Referring back to our previous discussion - I think you're referring to a bit error type of failure rather than a physical device failure.

    MTBF for my products is related to the physical failure of the device -- ie an internal trace wears out, or hot carrier injection produces too much of a shift in threshold.

    It's unrelated to the digital operation and possible errors therein.

  • 0 in reply to Emrys Maier
    TI__Expert 5483 points

    Hi Emrys,

    I see...yes, I have been trying to discuss bit error failures, which require device characterization data to calculate.
    Does this mean we don't have any characterization data that could be used to calculate τ and t0 for this device?

    From the app note, the author seems to have suggested this characterization exists...at least for some devices; as he gives a simple method of testing for it. 

  • 0 in reply to Darren (FAE)
    TI__Guru* 96591 points

    That is correct -- this device is a relatively simple analog circuit. If you provide the correct setup and hold times, the output will be correct. If you don't, we can't guarantee anything (and that's the main area the app note discusses - metastable states).

    In other words, if you violate the datasheet spec, we don't guarantee functionality.