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Second breakdown in SOA

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Hiroshi
Hiroshi Wolfspeed Employee - Contributor Level 2
edited June 2023 in Discrete Products

Hi Wolfspeed expert,

 

I have a customer using Wolfspeed’s 1200V discrete SiC MOSFET. They’re reviewing the datasheet and fond there’s no second breakdown region of SOA.

Could you please explain more detail why Wolfpseed’s SiC MOSFET does not have second break down region? What’s the difference between Si power devices?

 

Thank you for your support.

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  • Forum_Moderator
    Forum_Moderator Wolfspeed Employee - Contributor Level 5
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    Thank you for your post, it has been approved and we will respond as soon as possible.

  • jshao
    jshao Wolfspeed Employee - Contributor Level 2
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    Hi Hiroshi,

    The secondary break phenomenon only happens to bipolar device. In MOSFET, secondary breakdown does not occur, because it has positive temperature coefficient. What is the application of your customer, where they have concern over SB?

    Sometimes thermal instability for MOSFET can happen in the linear region when Vgs is low. During that mode, current can concentrate in certain area and cause damage. Wolfspeed doesn't recommend customers to operate SiC in linear mode, so there is no concern for this issue.

    Thanks,

    Jianwen

  • Hiroshi
    Hiroshi Wolfspeed Employee - Contributor Level 2
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    Hi Jianwen,

    Thank you for the explanation. The application is OBC. The customer is concerned that variations in Vth within the chip may cause a localized current concentration that may result in thermal runaway.

    (current concentration to low Vth cell -> temperature rise -> Vth decrease -> current concentration -> ...).


    I think it is possible that Vth variation within the chip may increase due to short channel effect caused by cell shrink. But is it correct to understand the Vth variation does not occur in current SiC MOSFET because of larger cell size vs Si MOSFET?


    Best Regards,

    Hiroshi

  • jshao
    jshao Wolfspeed Employee - Contributor Level 2
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    Hi Hiroshi,

    This current concentration issue can cause failure only when the device stays in the condition( Vgs is slightly higher than Vth) in long time (us or ms). For switching application, the time is so short, there is no problem for this to happen.

    Best Regards,

    Jianwen

  • Hiroshi
    Hiroshi Wolfspeed Employee - Contributor Level 2
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    Hi Jianwen,

    Thank you for your comment and I understood. Let's close this discussion.

    Best Regards,

    Hiroshi

This discussion has been closed.