• State Answer Suggested
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 14 subscribers
  • Views 80 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISO1211: fault addressed in the FMEA

Daria Kiseleva
Intellectual 2325 points
Part Number: ISO1211
Other Parts Discussed in Thread: TIDA-01599, ISO1228

Tool/software:

Good day, collogues, 

My customer would like to use the ISO1211 for an STO circuit. They have reviewed the documents “Overview STO Concept TIDA-01599” and the associated FMEA “FMEA_STO_Concept_TIDA-01599.xlsx”. And have a question regarding a fault that is also addressed in the FMEA. What happens in the event of an interruption of the FGND, for example, due to a break in the wire at the terminal?

The FMEA simultaneously assumes that INx and SENSEx are open.

However, this does not necessarily have to be the case. There could still be a voltage present at INx and SENSEx. This scenario is not covered in the FMEA, hence my question. Is it also guaranteed in this case that the output will go to logical low?

Additionally, I am interested in what happens in the case of an unstable connection to FGND. For example, if the connection is frequently disconnected and reconnected due to an improper connection at the terminal during vibrations. Is it ensured that the output remains at logical low in this case?

Thank you,

Daria

  • 0
    Guru 296890 points

    The input side of the ISO121x is powered by the current that is flowing through it. (This is similar to a classic optocoupler, which is active when a current flows through the input LED.) When no current flows (either because the input voltage is low, or because the connection is broken at some point), then the output is in the default state (low).

    From the point of view of the ISO121x, an unstable connection looks like a signal that is only sometimes active. The datasheet guarantees that a pulse width of at least 150 ns will be detected; shorter pulses might or might not get through.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24245 points

    Hello Daria, 

    In addition to Clemens comment, I would like to point out that ISO1228 includes a wire-break detection feature for sink mode inputs. ISO1228 may be helpful for your applications if you are looking to detect a broken connection at the input. Otherwise, ISO121x will simply return to a default state if the connection is broken. 

    Best,
    Andrew