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UCC5350: UCC5350M Vout-VEE2 negative voltage

Yishan Chen
Prodigy 195 points
Part Number: UCC5350
Other Parts Discussed in Thread: ALLIGATOR

Hi,

Customer want to evaluate the risk about negative voltage between Vout to VEE2 pin.

The negative voltage will occur in the MOSFET transition duration. Here is the waveform.

The maximum negative voltage in turn-off is -1.68V, Duration is about 5.6ns. Will there any risk?

Is there any way to reduce the negative voltage? 

Turn-on

Best Regards,

Yishan Chen

  • 0
    TI__Genius 14206 points

    Hi Yishan,

    Are you using your Miller clamp with 0 ohms? Can you show me a schematic image?

    Your voltage is ~5ns and it is resonating. I think that the bond wire inductance is enough to isolate this voltage from the driver die. The output stage is a closed switch, and can sink lots of power without damage.  

    Just to confirm, I configured an extreme test for UCC5350 that injected maximum Miller current into the output (high-side driver in a half bridge). I measured the gate driver output with an isoVue probe.

    I was able to sink enough transient current to drop the output to -5V for ~100ns, and there was no damage to the driver (image below).

    Best regards,

    Sean

  • 0 in reply to Sean Cashin
    TI__Prodigy 195 points

    Hi Sean,

    Thank for your support. Here are the schematic, I assumed the clamp resistor is 0ohm.

    So according to your reply, there are nothing we need to worry about. Right?

    But I still want to know do we have any way to reduce the negative voltage.

  • 0 in reply to Yishan Chen
    TI__Genius 14206 points

    Nothing to worry about so far. I bet most of this resonance could be eliminated by using a more rigorous probe circuit.

    In my measurement, I used an IsoVu probe with an MMCX connector. The alligator clip ground sometimes picks up more ringing than is present.

    You can eliminate real ringing by improving the supply decoupling. The output should be effectively shorted to either power supply rail most of the time, except for some bond wire inductance and trace inductance between the output and the supply. 

    Best regards,

    Sean