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  • TI Thinks Resolved

ISO1212: Has ISO1212 fail-safe?

Part Number: ISO1212

Hi, Expart

My customers are demanding products with fail-safe function.

Does ISO1212 have a fail-safe function (double insulation structure)?

We are considering replacing the 24Vin photocouplers.

Best regurds

Takakura

  • Hi Takakura-San,

    Could you please explain a bit more on what is required with the fail-safe function? What type of stress test is expected on the device?

    To answer your question, ISO1212 has a single insulation structure. But we don't usually see this requirement of double insulation being asked for this particular part.

    To help us understand better, could you please share the end application and the part number of photocoupler you are looking to replace?

    Thank you for helping us with this requested data. It would help us understand the requirements better.

    Regards,
    Anand Reghunathan
  • In reply to Anand Reghunathan:

    Hi Takakura-san,

    ISO121x meets 2.5 kVRMS for 1 minute, and 6 kV surge. This is more than sufficient for isolated 24-V digital input modules that see only a max of 36 V. Double insulation is not a requirement for <50-V systems.

    On the other hand, there are several benefits the ISO121x offers: www.ti.com/.../slla370. Please let us know if the customer still has any concerns.

    Rgds,
    Anant

     

     

  • In reply to Anand Reghunathan:

    Hi Anand Reghunathan-san

    Thank you for quick replay.

    First of all I would like to know if it becomes "open" when the insulation part of ISO 1212 breaks down?
    My customer is most concerned about being Short, because photo couplers are absolutely not short.
    For other characteristics such as isolation , we are satisfied with basic insulation.

    The target application is "Machine Tools" , in this case many photo couplers used, which pass a signal with a sensor output voltage of 24V.

    Regards,
    Takakura
  • In reply to koki takakura:

    Hi Takakura-san,

    The insulation of ISO1212 can break down under two kinds of stress conditions:

    1. If the voltage rating across the barrier is exceeded: 2.5kVRMS for 1 minute or 6 kVpk surge. This condition never occurs in a 24V system.

    2. If there is overvoltage on the 24V input causing overheating inside the chip. In this case, ISO1212 is designed to handle +/-60V operation in normal operation . This is the maximum voltage that can usually occur in a 24-V system. Hence damage to insulation of ISO1212 due to overheating is also prevented.

    I hope this helps solve customer's concerns.

    Please also take a look at http://www.ti.com/lit/an/slla370a/slla370a.pdf. This tech note highlights how ISO1212 can offer various advantages when compared to existing solutions in market.

    Regards,
    Anand Reghunathan

  • In reply to Anand Reghunathan:

    Hi Anand Reghunathan-san

    Thank you for replay.

    I understood what your saying. But My Customer want to know is a bit different.

    [Question]

    What happens to the output when an abnormality occurs in ISO 1212?

    1. High   2.Low   3.Open   4.Unknown   

    Best Regards,

    Takakura

  • In reply to koki takakura:

    Hi Takakura,

    If there's any abnormality on the field or 24-V side, the ISO1212 outputs on the 3.3V/5.5V side will always be "Low".

    Rgds,

    Anant

     

     

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