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TPS76701-EP: TPS76701-EP

Silvia Ferreira1
Prodigy 110 points
Part Number: TPS76701-EP

In the data sheet, it is stated that recommended operating virtual junction temperature is 125ºC and that it is not recommended that the device operates under condition beyond that temperature for extended period of time. However, there is a thermal shutdown junction at 150ºC.
- How much is considered a extended period of time? Will be 24 hour working OK operating over 125ºC and under 150ºC?
- If it is operated beyond 125ºC and below 150ºC, with periodicity, for instance 8 hours over 24h, every day over three months is the "extended period of time" affected? That is, if we say that the extended period of time (considered as continuous) is 24 hours, but the part is used 8 of the 24 hours for a longer duration (3 months for instance), will the part "die" ahead of time?
- The shutdown junction is 150ºC: is this the real junction limit ,where the silicon breaks, or because the part design internal limitations the real junction maximum operation will be 125ºC?

  • 0
    TI__Mastermind 37065 points

    Hi Silvia,

    What you are asking is related to the reliability of the component.
    As you increase the temperature of a component, the mean time before failure (MTBF) decreases.
    The relationship between increased temperature and decrease in MTBF is well known in industry, and TI has built some tools to help assess it for our customers.

    Please see the following link for additional details on Quality and Reliability data.

    https://www.ti.com/qualificationsummary/qualsumm/home?actionId=2800

    Please see the following calculator to help you understand what the reliability for your device will be with increased temperature.

    http://www.ti.com/support-quality/reliability/temperature-change-FIT.html

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 110 points

    Hi Stephen,

    Thanks a lot for your answer. We are aware of these formula.

    The question was really more oriented to know the maximum juntion temperature of the device. I understand it is Tjmax shutdown = 150ºC.

    I would like to confirm also that the life test (1000 h) was done at Tj=125ºC. It is not specified if it was Tj or Tc, even if it is inferred by the device type.

    The question comes from the fact we foresee to use the device at around 135ºC, but the note on recommended operation temperature + the fact that tjmax shutdown is not a typical parameters, put the questions we try to clarify:

    - The note:  Continuous current and operating junction temperature are limited by internal protection circuitry, but it is not recommended that the device operate under conditions beyond those specified in this table for extended periods of time.

    -->  will the part shutdown if used at Tj>125ºC due to the internal protection? When?

    Thanks

  • 0 in reply to Silvia Ferreira1
    TI__Mastermind 37065 points

    Hi Silvia,

    The component has a typical thermal limit which kicks in at 150C. 
    I'm not able to find a tolerance on this parameter, but it is fairly common to only have a typical thermal limit temperature.
    The thermal limit circuit is a protection circuit and will shut down the component when the junction reaches that temperature.
    The note you described is stating that we do not recommend operation at this elevated temperature where protection circuitry kicks in.

    In sum, the component will operate up to 125C, but beyond this temperature it may hit thermal limit.  It typically hits thermal limit at 150C.

    Keep in mind that if you exceed 125C junction temperature, the datasheet parameters are not guaranteed, as they were characterized from minimum temperature to 125C, not 150C.  So tolerances will increase slightly and we recommend that you verify the functionality of the linear regulator meets your needs.

    The temperature that the life testing was conducted at was 125C.
    Please see the following link. 
    There is a lot of information in those links that I've provided.
    You can also find information like this in the product folder (aka the TI website for this device), but it will send you to these links.

    http://www.ti.com/quality/docs/estimator.tsp#resultstable

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    TI__Mastermind 37065 points

    Hi Silvia,

    I see this response did not answer your question.
    I believe I have answered each of your concerns, but please reply back and let me know if you need additional support.

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 110 points

    Hello Stephen,

    There is something I don't understand, but likely due to ignorance (I apologize)

    In general, data sheets show Tjmax (absolute maximum junction temperature), which is the typical thermal limit due to physical material limits. However, in this particular case, TI makes a difference between the virtual maximum junction temperature and the shutdown maximum junction temperature. Is this maybe because despite the maximum Tj is given at 125ºC, the device could work at Tj<150ºC but with unknown performances? Why this difference is not made for other devices (due to the internal design, maybe)?

    On the other hand, for the temperature change FIT calculator, I would like to check which DPPM should I write to make the calculations; I wrote 28,20, value given considering 32495 on sample size and 60% CL, on http://www.ti.com/support-quality/reliability/DPPM-sample-size-calculator.html,

    The figures I obtained on your calculator  differ slightly  from the ones applying Arrhenius to 0.4 FIT @ Tj = 55ºC

    Thanks a lot for your help

  • 0 in reply to Silvia Ferreira1
    TI__Mastermind 37065 points

    Hi Silvia,

    Your question is not due to ignorance.
    I don't think the "virtual maximum junction temperature" is a common term.
    In fact, this has been asked before by your colleagues.
    See the following E2E post from 5 years ago:

    https://e2e.ti.com/support/archive/internal/int-linear_regulators/f/324/t/394022?tisearch=e2e-sitesearch&keymatch=TPS76701-EP

    From the research in that forum, I think the terms "virtual junction temperature" and "junction temperature" can be used interchangeably.

    I looked at the Arrhenius calculator and I think I see what you are seeing.
    I set the Application and Qualification temperature sliders to 125C.
    When I type in DPPM = 0.350000001 I get MTTF = 2.5e+9.
    When I type in DPPM = 0.35 I get MTTF = 3.33e+9.
    It's almost like there is a lookup table, and it uses the entry in the DPPM box and rounds to the nearest value.
    I would use this calculator as an estimate but the value in the qualification data is what is accurate.

    Here is how I entered the data - again, I think the online tool is probably using a lookup table.

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    Prodigy 110 points

    Hello Stephen,

    I cannot access the link you pasted, it prompts this message:

    - My question on shutdown maximum junction temperature has not been answered (maybe was in the link, but as it is not accessible):

            - What is the concept of shutdown maximum junction temperature?

            -  Despite the maximum Tj is given at 125ºC, the device could work at Tj<150ºC but with unknown performances?

             - Why this difference (virtual Tj and shutdown Tj) is not made for other devices (due to the internal design, maybe)?

    Thanks for the rest of answers

  • 0 in reply to Silvia Ferreira1
    TI__Mastermind 37065 points

    Hi Silvia,

    The device may operate above 125C but only until it hits thermal protection. 
    That can be immediately above 125C or close to 150C, or anywhere in between.
    The lifetime as we have discussed will be reduced and the datasheet performance would not be guaranteed at these elevated temperatures.
    We have not characterized the performance above 125C.

    I guess that forum is internal only.
    I copied and pasted the relevant information below from that forum.

    "... virtual junction temperature ..."

    Search E2E and you will get a number of hits for this term.

    JEDEC has a definition, and I generally point to the NOTE in that defintition:

    http://www.jedec.org/standards-documents/dictionary/terms/virtual-junction-temperature-internal-equivalent-temperature-tj

    ------

    Virtual-Junction Temperature; Internal equivalent temperature (Tj; Tvj)

    (1) A temperature representing the temperature of the junction(s) calculated on the basis of a simplified model of the thermal and electrical behavior of the semiconductor device.

    NOTE: The term "virtual-junction temperature" is taken from IEC standards. It is particularly applicable to multijunction semiconductors and is used to denote the temperature of the active semiconductor element when required in specifications and test methods. The term "virtual-junction temperature" is used interchangeably with the term "junction temperature".

    (2) The temperature of the virtual junction

    Thanks,

    - Stephen