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TMCS1123: Isolation Failure Modes

Conor
Guru 12050 points
Part Number: TMCS1123

Tool/software:

Hi,

We are currently evaluating the TMCS1132 in a safety-critical application, and would like to request technical input regarding its isolation failure modes.

Specifically, we would appreciate any available documentation or insight on the following:

  • Typical failure modes in the event of isolation barrier breakdown (e.g., short circuit, leakage current, thermal effects)

  • Possible electrical connection between primary and secondary sides in such failure events

  • Whether any fail-safe mechanism exists internally to mitigate isolation failure effects

  • Any known failure mechanisms considered during UL/IEC safety certification tests

Understanding the behavior under isolation failure is critical for assessing risks in the system.

Thanks,

Conor

  • 0
    TI__Expert 5320 points

    Conor,

    Thanks for the question and using the E2E forum.

    Due to the U.S. holiday on July 4, we are currently out of the office. Someone will reply when we return on Monday, July 7.

    Thank you for your patience.

  • 0 in reply to Louis L
    Guru 12050 points

    Hi Luis,

    Okay, I'd love to hear your feedback.

    Thanks,

    Conor

  • 0 in reply to Conor
    TI__Mastermind 22275 points

    Conor, 

    For functional safety, this is typically handled by our "-Q1" devices. In the product folder for the TMCS1123-Q1, you can find FIT and FMA information for the device. However, we do not include this data in the report, as short circuit across the isolation barrier can be excluded according to IEC 61800-5-2:2016 if the following requirements are fulfilled:

    1. The signal isolation component is OVC III according to IEC 61800-5-1. If a SELV/PELV power supply is used, pollution degree 2/OVC II applies. All requirements of IEC 61800-5-1:2007, 4.3.6 apply.

    2. Measures are taken to ensure that an internal failure of the signal isolation component cannot result in excessive temperature of its insulating material.

    These criteria apply to the TMCS123-Q1, so this should be able to excluded from analysis. Is there a standard beyond IEC61800 you are attempting to meet here?

  • 0 in reply to Carolus Andrews
    Guru 12050 points

    Hi Carolus,

    Sorry, my question may be unclear and you may have misunderstood.

    For example, the following manual is provided for TI's Isolator.
    https://www.ti.com/lit/wp/slyy081b/slyy081b.pdf

    Is there a document on the failure mode for each failure case, like this manual?

    Or does this manual also apply to the TMCS1123?

    Thanks,

    Conor

  • 0 in reply to Conor
    TI__Mastermind 22275 points

    Conor, 

    Got it. Unfortunately we have not published a full guide similar to the one you point out. These use capacitive and optocoupled topologies, where our devices utilize Hall effect to transmit information across the isolation barrier. This comes with certain differences inside the part (although the process is quite similar to the described optocoupler). I will provide feedback to our systems team that such a document could be useful here in addition to the guidance I provided above.