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Original question:

TPS3703-Q1: Glitch immunity to sensor pin at UV/OV

TPS3703-Q1: Glitch immunity (tGI) vs. detect propagation delay (tPD)

Andreas Nestler
Intellectual 310 points
Part Number: TPS3703-Q1

Hello, I'm struggeling a bit with the parameters sense glitch immunity (tGI) and detect propagation delay (tPD). How are both related to each other? If we consider e.g. an undervoltage / overvoltage condition for 100us and measure the time from start of out of range condition (UV / OV) until the RESET output is going to Low level then we have measured  the parameter tPD. If the pulse would be shorter than the measured time then the output would not switch to Low level. In this case we would have determined the glitch immunity, wouldn't we? If my assumption is wrong what would be the correct way to evaluate the glitch immunity via test?

Many thanks in advance!

Best regards,

Andreas N.

  • 0
    TI__Genius 11470 points

    Hi Andreas,

    Thank you for your question. The sense glitch immunity (tGI) is the time needed to verify if the fault is not a glitch, while tPD is the time needed for RESET to react to the valid fault from the SENSE pin. In application tGI and tPD elapse in parallel, with time starts when a fault is detected. If the fault duration is shorter than tGI, RESET will not assert after tPD. If fault duration is greater than tGI, RESET will assert after tPD. The image below illustrates this behavior, but instead of MR, view it as UV Sense.

    Jesse 

  • 0 in reply to Jesse Villanueva
    Intellectual 310 points

    Hi Jesse, thanks for the valid information. Still I have some question reagrding this.

    1) If I understand the figure correct the time tGI is shorter than tPD. If I'm looking into the datasheet, this does not match with the data presented there, at least with the graph data.
    tPD is shown in figure 7-22 and the tGI is shown in figures 7-11 to 7-14. In the table in section 7.6 tPD is specified with 30us max.

    2) What is the source of the shown figure? Datasheet has this type of diagramm but without the tGI information (Figure 8-2 in section 8.3.5)

    3) Can you confirm that the the presented graph from datsheet for MR is applicable for SENSE as well?

    4) Finally, can you confirm that we cover tGI if we measure tPD? I know from your statement that the time tGI will be less than tPD. But if tPD fullfills our timing requirements that is fine and there is no need to determine tGI.

    Thanks in advance again!

    Best regards,

    Andreas N.

  • +1 in reply to Andreas Nestler
    TI__Genius 11470 points

    Hi Andreas,

    1) Yeah, I just notice that too. The plot scales are off and should be fixed on the next revision of the datasheet. In general, the Glitch immunity is shorter than propagation delay. An example of this exception are devices with programmable sense delays.

    2) The Image is from 8-2, I had to edit the image to give a visual example. 

    3) Yes, I can confirm the behavior is applicable to SENSE as well.

    4) Yes, accounting for tPD is sufficient.

    Jesse 

  • 0 in reply to Jesse Villanueva
    Intellectual 310 points

    Hi Jesse, thank you very much for your dedicated answers.