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THVD2410: About A-B TVS spec

Jimmy WANG
Genius 4085 points
Part Number: THVD2410

Tool/software:

Hi team,

I saw the THVD2410 Typical schematic. suggest the TVS is 30V. Is 30V the specification because the industrial voltage is 24V?

Is system power is 48V. Need to change to 50V up TVS? thanks 

  • 0
    Guru 316920 points

    A short to the power rail is not a transient; a DC voltage above the TVS breakdown voltage would burn out the TVS. So the TVS should be rated for voltage higher than the power rail(s) that you are using in the cable. (If it is not possible in your application that the A/B data lines can be shorted to a power line, then this does not matter.)

  • 0
    Genius 4085 points

    Hi Team,

    OK Got it. But why the Fig9-6 use 30V TVS? as you mention just use a voltage higher than the power rail(s). Maybe 10V?

  • 0 in reply to Jimmy WANG
    Guru 316920 points

    The text above figure 9-6 says that this example assumes that there is a 24 V power rail near the RS-485 data lines. For 5 V power, you should indeed use a TVS for a lower voltage.

  • 0 in reply to Jimmy WANG
    TI__Genius 13752 points

    Hi Jimmy,

    It is correct that TVS diodes are for short transient events. Long sustained shorts will likely break the diode. The SMAJ30CA was recommended for short to battery conditions that were for brief periods of time. If you do not anticipate a short to battery condition, this should not be a concern. 

    If you desire ESD transient protection, I would recommend the ESDS552 which is rated for 12V working voltage. 

    Best,

    Ethan