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Original question:

TPIC71002-Q1: Running diagnostic tests periodically

TPIC71002-Q1: Diagnostic tests

Mario Kodba
Prodigy 20 points
Part Number: TPIC71002-Q1

Hi TI,

following up on previous discussion regarding diagnostic tests I have few more questions.
Table 11. on page 43 gives list of various diagnostic tests that can be performed. Some of them are pretty self-explanatory, but I would appreciate if you could give me more information about expected values, what is their usage, should they be run on start-up only or periodically, for the following tests:

  1. Gage measurement RSQREF
  2. Gage measurement VGAGE
  3. Gage measurement VOFFS 
  4. 1k squib measurement 1SLSA GAGE
  5. 1k squib measurement 2

BR,
Mario

  • 0
    TI__Mastermind 44315 points

    Hi,

    Thank you for your question regarding TPIC71002. No further summarized lost/information such as expected values for each settings. We would like propose to refer "ACTIVATED SWITCHES" on table 11 and Fig 20 Diagnostic block diagram for each settings.

    regards

    Shinya

  • 0
    Prodigy 20 points

    Sorry for the late response,
    I have read the table and seen figure that you mentioned but I do have few additional questions.
    1. What is the purpose of that reference resistor connected to terminals SQREF1 and SQREF2? We have successfully activated squib and current pulses seem fine so is that reference resistor really needed and are above mentioned diagnostic tests related to it (Gage measurement RSQREF, 1k squib measurement 1SLSA GAGE, 1k squib measurement 2) needed to be performed at all?
    2. Which tests on Table 11. should be performed periodically and which only at start up?

    thank you and best regards,
    Mario

  • 0 in reply to Mario Kodba
    TI__Mastermind 44315 points

    Hi,

    thank you for your post. Let me review this and feedback to you by July 2nd.

    regards

    Shinya

  • 0
    TI__Mastermind 44315 points

    Hi, 

    Let me reply as follows. 

    1. The reference resistor /known resistor (RQSREF) is connected between terminals SQREF1 and SQREF2 in order to estimate the unkown resistance of the squib/pyro. Please see the equation below.

    1K gage measurement might not be applicable for pyro applications. If this path is kind of open load between Zx and ZMx pins ( a resistance that can be as high as 1K ), the 1.5mA current source is used.

    For latest airbag ICs, this 1K gage measurement is not used anymore to my knowledge.

    TPIC71002.pptx

     2.The HS switch test and LS Switch test are performed at start up. The rest of the tests like voltage measurement, leakage measurement and resistance measurements are done periodically

    regards

    Shinya

  • 0 in reply to Shinya Morita
    Prodigy 20 points

    Great, thank you, this clarifies things a little bit. I'm still not sure what is the difference between running RQSREF + "Squib resistance" test as mentioned in pptx you have given to determine squib resistance and using only "Squib resistance" test in Table 11.

    Currently we run "Squib resistance" test with 20mA setting, we get V_amx_out voltage (formula given in your pptx) and we determine the squib resistance R_squib as:
    R_squib = V_amx_out / 20mA
    Shouldn't this give same squib resistance (R_unknown) as steps described in your pptx or we are doing it wrong?

    Also, is there a difference in result between running "High voltage measurement VA1" and "High voltage VA1 measurement with high side current source enabled"?

  • 0
    TI__Mastermind 44315 points

    Hi,

    thank you for your post. Let me review this and feedback to you by July 8th.

    regards

    Shinya

  • 0 in reply to Shinya Morita
    TI__Mastermind 44315 points

    Hi,

    Thank you for your post. Unfortunately I could not find further details about your questions. Hopefully information what we provided so far can be used.

    regards

    Shinya