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Original question:

ISOW1432: ISOW1432 VISOOUT power supply

ISOW1432: surge

Hector Chen
Intellectual 330 points
Part Number: ISOW1432

Hi Team,

I would like to confirm the surge level of ISOW1432B. Can it withstand 10/700us waveform at +/-1KV with 27.5 ohms coupling (EN55035) without damage and affecting function and communication?

Can we feel safe to not add any TVS or series resistors on the trace for transient protection?

Datasheet mentioned ISOW1432B can pass 7.8KV surge voltage, can it pass without affecting the functions of ISOW1432B?     

Thanks

  • 0
    Intellectual 330 points

    Hi Team,

    Can you briefly explain how you test surge? Did you connect A, B, Y, Z and GND2 (as the return) to a surge generator?

    Absolute Maximum Ratings table shows voltage on bus pins (A, B, Y, Z with respect to GND2) should be within -12 ~ 15V.

    Does this mean common mode operation rating, not electrical transient rating?

    Thanks.  

  • +1 in reply to Hector Chen
    TI__Guru 53715 points

    Hi Hector,

    Thanks for reaching out.

    ISOW1432 is an isolated RS-485 with integrated DC/DC converter and the Surge rating is specified as part of isolation specification in Section 8.5 of ISOW1432 datasheet titled as "Insulation Specification". This indicates the Surge rating is for the isolation barrier of ISOW1432 and not for the RS-485 transceiver. i.e., it is rating that the device will support between GND1 and GND2.

    The test setup is similar to what is shown in the figure below where the stress is intended to be applied to isolation barrier and not to any other low voltage components in device.

    The RS-485 transceiver in ISOW1432 doesn't have in-built protection against Surge testing on the bus, you would need to add external protection components to meet your application Surge requirements.

    Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao