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UCC21732QDWEVM-025: DESAT Protection diode's purpose?

Sivakumar Dumpala
Prodigy 20 points
Part Number: UCC21732QDWEVM-025

Tool/software:

I have seen two diodes (D5 and D6) for DESAT protection. What exactly the purpose of two over one diode?

  • +1
    TI__Expert 8125 points

    Hi Sivakumar,

    Are you talking about the high voltage diodes (D5, D6 below)? . As the drain /collector node is High Voltage, these HV diodes help to protect the DESAT pin being exposed to HV and also will help to conduct DESAT node "charge current" when the power switch is working in normal condition. In case of Short circuit event, the voltage across the power FET will be higher and it will cause the diode to be reverse biased and it will stop conducting which will increase the DESAT blanking capacitor (c20) voltage. 

    Please find the following Article which talks about the DESAT functionality in detail . Hope it helps.

    [E2E FAQ] Adjusting DESAT Threshold

  • 0
    Prodigy 20 points

    Hi Sasikala,  Thank you for the clarification.

    Also please let me know the need of the three diodes (Zeners and Schottky) with different ratings and how they are useful in DESAT and other Protection.

  • 0 in reply to Sivakumar Dumpala
    TI__Expert 8125 points

    Hi Sivakumar,

    The Zener diode is  to limit DESAT node voltage to be ~12V as planned by Zener threshold (typically 12V)

    The Schottky diode is  to limit COM node going higher potential compared to DESAT node.

    Hope it helps.

    Thanks

    Sasi