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THVD8000: BUS I/O Fault Protection Behaviour

Maximilian Dörsch
Prodigy 20 points
Part Number: THVD8000
Other Parts Discussed in Thread: THVD8010

Tool/software:

Hi Team, 

I have a question about the behaviour of the THVD8000.
The data sheet specifies a bus I/O fault protection of +/-18V DC.

How does the module behave if I get a voltage increase >18V at input A and B due to a surge pulse?
What does fault protection mean in this case?

Thanks. 

Best Regards

Max

  • +1
    TI__Guru 52282 points

    Hi Max,

    This device is not surge rated - we'd suggest adding external surge protection between THVD8000 and series coupling caps if it is a concern when using the THVD8000 or THVD8010.

    The +/-18V is the DC fault level max - there could be some leeway for short transients (ESD and EFT - this device is rated for ESD and EFT protection - see below)

    However - as mentioned it isn't surge rated (no IEC 61000-4-5 rating) - so external protection is needed. 

    Traditionally - and most commonly - this takes the form a surge diode + a small pulse proof series resistance between output of transceiver and rest of bus - for THVD8000 it would lie before capacitive coupling network. However depending on specific application something more robust may be needed - please take a look at this design guide on protection for RS-485 - the THVD8000 is almost fully compliant with RS-485 so a lot of the techniques used in RS-485 can be applied to THVD8000/THVD8010. 

    https://www.ti.com/lit/ug/tiduas1b/tiduas1b.pdf?ts=1737731582207

    Please let me know if you have any further questions. 

    Best,

    Parker Dodson