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Original question:

UCC21750: VCC 5V is better than VCC 3.3V

UCC21750: Shottky & Zener will increase the blanking time

Anoop kumar N
Intellectual 998 points
Part Number: UCC21750

Hello,

While testing the DESAT protections, it is found that the zener & shottky diode placed across the OC pin can increase the blanking time little bit more. when we removed and tested we found improvements in turn of time. result. For 35A SiC mosfet, the SOA is limited and saving even a 50 to 100s of nanosecond time is very important for us. So designing a desat circuit for a low current rating mosfet is a challenging one ? since the rate of rise current is determined by the board parasitic inductance and we need to tune the DEsat such that its SOA should not violate for the given board parasitic's di/dt. Ryt ?

So zener & Shottky are mandatory ? 

Thanks and regards

Anoop

  • +1
    TI__Expert 7473 points

    Hi Anoop,

    Thanks for the post. UCC21750 has a DESAT pin. Designing the DESAT circuit for SiC MOSFET in general has to be done cautiously since the short circuit withstand time of SiC MOSFETs are very less compared to IGBTs. 

    As you see the zener and shottky are recommended for protection and not required/mandatory. Hence if your environment doesn't need OV/ Negative transient protection, you should be fine without them.

    Hope this helps!

    Best,

    Pratik