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ISO5451: Power management forum

Marco Esposito
Prodigy 10 points
Part Number: ISO5451

Hello community,

I have a problem with the DESAT connector on the gate driver ISO5451. As shown in the simulation result, the voltage value drops to -1.8V. I suspect an error in my circuit diagram. But unfortunately I can't find it. The output of the gate driver behaves correctly. The IGBT is switched through correctly. Only the DESAT connection gives me a headache.

Maybe someone can help me in this regard. Thank you very much.

  • 0
    TI__Expert 5530 points

    Hi Marco,

    Thank you for choosing ISO5451 driver.

    I had a quick check on your schematics.  I dont see anything wrong with the overall implementation.

    I would recommend trying an ideal Diode on the DESAT path - the capacitive effect of the diode might cause the DESAT pin to go low.

    Also as given in datasheet, 

    Switching inductive loads causes large instantaneous forward voltage transients across the freewheeling diodes of the FETs. These transients result in large negative voltage spikes on the DESAT pin which draw substantial current out of the device. To limit this current below damaging levels, a 100-Ω to 1-kΩ resistor is connected in series with the DESAT diode. Further protection is possible through an optional Schottky diode, whose low forward voltage assures clamping of the DESAT input to GND2 potential at low voltage levels.

    So you can also plan a Schottky diode on the DESAT pin to clamp the voltage to GND2 potential.


    Thanks

    Sasi