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ISO3086T: EMC Protection at BUS

Priyansh Kharote
Prodigy 40 points
Part Number: ISO3086T
Other Parts Discussed in Thread: STRIKE

As in EMC testing transience will be applied with reference to non Isolated GND (GND1) is there any method to calculated clamping volttage of TVS connected for protection ?

Also, in datasheet allowable maximum voltage at BUS is given with reference to  GND2. So in case of EMI transience (wrt GND1) what will be allowable voltages BUS pins (A,B, Y, Z) ?

  • 0
    TI__Mastermind 48215 points

    Hi Priyansh,

    Thanks for posting your question here and welcome to E2E!

    I can't see the image you shared, would you please try to post it again?

    The isolation barrier in ISO3086T isolates all pins on each side of the device to the opposite-side ground (and all other pins on the opposite-side). In the case of the BUS pins (A, B, Y, Z), the maximum transient isolation voltage across the device (with respect to GND1) is 4242 Vpk (see Section 8.3.1.2 on datasheet). This means if the transient voltage is expected to be less than this value, no external protection is necessary.

    Because isolated systems have separate grounds, TVS diodes cannot provide protection in the same way as they would in non-isolated systems. This is because the energy in an across-the-barrier strike is presented as common mode to “single-side” or “local” ESD protection. A local TVS diode would not clamp due to a large voltage difference between isolated ground planes. Because of this, isolated systems rely on the digital isolator to withstand transients which might otherwise be clamped using protection devices such as TVS diodes. 

    I hope this information helps. Let me know if you have any other questions.

    Regards,
    Eric