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LM74610-Q1: How to choose correct TVS if the nominal voltage is 18.5V?

Karlis Tucs
Expert 1385 points
Part Number: LM74610-Q1
Other Parts Discussed in Thread: LM74700-Q1

Hi everyone.

So I wanted to impelment LM74610-Q1 in my design but I am in dead end, I guess.

voltage applied to circuit is 18.5V. Maximum negative voltage of LM74610-Q1 is -45V.

This means that the TVS which is responsible for negative voltage spike suppresion should clamp voltage at 45-18.5 = 26.5V minimum.

Any TVS diodes that I look up which clamps at this voltage has working voltage of lower than 18.5V, which means it would start breakdown if voltage is applied with reverse polarity.

Is my only solution now to choose something like LM74700-Q1 or is there still some solution with LM74610-Q1 ?

Best regards,

Karlis Tucs

  • 0
    TI__Genius 16305 points

    Hi Karlis,

    At 18.5V, during negative ISO test pulse 1, cathode can be at 18.5V and anode should not go below -(45-18.5) = -26.5V.

    With SMBJ type of TVS, it is not possible to meet both clamping voltage and breakdown voltage requirements.

    We strongly recommend using LM74700-Q1.

    This device is in preview mode and preliminary samples are available now from TI Store.

    However, if you are looking for a device that is released, like LM74610-Q1, as an alternative, you could use SMCJ series with LM74610-Q1.

    SMCJ18A breakdown voltage is 22.1 and clamping voltage at 15A surge current would be about 24.5V.

    (Negative ISO pulse test 1, has -150V surge voltage with 10ohm surge generator impedance, this boils down to 15V surge current).

    Please refer to the blog:

    Let me know if you have questions still.

    Regards,

    Kari.

  • 0 in reply to Karikalan Selvaraj
    Expert 1385 points

    Ok, thank you.

    One more question: Are smallest quantities 1k from TI store?

    Best regards,

    Karlis Tucs

  • 0 in reply to Karlis Tucs
    TI__Genius 16305 points

    Hello Karlis,

    Let me check on that and get back.

    Regards,

    Kari.