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ISO7841: ISO7841DWR maximum allowable Clamp voltage at ESD peaks

Part Number: ISO7841

Hi, 

I have a ESD diode at the power supply of IC ISO7841DWR. I need to confirm to what clamp voltage this IC can handle. The maximum allowable voltage per datasheet is 6V. But what if there is a peak at nano-seconds due to ESD. 

  • Hi Neha,

    ISO7841 supply and input/output pins are protected against HBM and CDM ESD pulses and the levels the device supports are listed in datasheet. I am copying below the ESD voltage levels supported by device. Let me know if you have any questions, thank you.

    Regards,
    Koteshwar Rao

  • Thank you Koteshwar for prompt reply. This image shows the HBM and Cdm Model specifying the manufacturing requirements, the same has been specified in datasheet

    I am trying to understand the requirement at peak current per IEC 60601-2-4. I have used a diode in parallel to the power pin of the IC. The diode has different clamp voltage at different current. 

    So the allowable maximum voltage that can be applied to maximum 100nsec. 

  • Hi Neha,

    Thank you for clarifying your requirements. HBM and CDM model of ESD requirements are usually defined for most integrated circuits to protect them against such ESD events occuring in a PCB assembly and test facility that have controlled ESD environment.

    I do not have access to IEC 60601-2-4 standard but I believe this is a standard for medical equipment. The ESD requirements defined in this standard must be system level ESD requirements that need to be tested according to IEC 61000-4-2 on external terminals and/or casing of the medical equipment. Since ISO7841 is only a digital isolator with CMOS logic input/outputs, this device terminals are usually not expected to be directly accessible for any system level ESD testing on the exterior of the medical equipment. For this reason, the digital isolators do not usually have any specific protection against system level ESD.

    Hence, using a diode (I believe you were referring to TVS diodes) might still not make the device protected against such system level ESDs as the clamping voltage of TVS diodes itself will have quite some variation that will exceed device absolute max ratings.

    I hope this answer the questions you had. If you still think your question is not answered, then please do explain more about your application, where exactly the ISO7841 is sitting in your application and what kind / level of protection needed on ISO7841 terminals. Thanks.

    Regards,
    Koteshwar Rao

  • Thanks Koteshwar, This gives quite an insight. 

    I was just wondering if voltage specified as maximum limit (6V in this case), is for DC voltages. And for peaks for around 100ns, the IC can sustain an higher voltage than 6V.

    Please correct me if I am wrong. 

    Regards

    NEHA

  • Hi Neha,

    The maximum recommended voltage to device supply pins is 5.5V while the absolute maximum ratings of the same is 6V. Please note that absolute maximum ratings are not the continuously operated voltage ratings, please see below the note from datasheet.

    Regarding the transient voltage performance, the device is designed to support transients like HBM and CDM which is also expected to lasts about 100ns. The device is not characterized for any other arbitrary transients and hence it would be hard for me to confirm if device supports such voltages.

    Please do let me know if there is any particular peak voltage pulse along with a duration that you need the device to support and also let me know how many  such events are expected to occur on device supply pins throughout its life, I maybe able to comment if device will be able to support it.

    Regards,
    Koteshwar Rao

  • Hi Neha,

    I am assuming your questions are answered, I will go ahead and mark this thread closed. If you still need any clarifications, then please do not hesitate to reply to this E2E post. Thanks.

    Regards,
    Koteshwar Rao