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LM5141QRGEVM: SW node ringing

Arie Li
Expert 3390 points
Part Number: LM5141QRGEVM

Hi team,

I was observing the voltage ringing at the switch node by using the EVM. I found the voltage overshoot and ringing is different at different input voltages. In my opinion, the ringing at VIN=12V(left figure）is much more common and easier to understand. But when the input voltage is 24V or much higher, the ringing become less obvious. It seems that the switching speed of the top switch is much slower? How does this phenomenon happen? Could you please give some explanation?

Thanks.

  

  • 0
    TI__Guru 53152 points
    Hi Arie,

    One factor is that the inductor ripple current increases at higher Vin, so the current at high-side MOSFET is lower and hence the energy stored in the parasitic switching loop inductances is reduced.

    Also, the power MOSFETs have non-linear parasitic capacitances, so their switching behavior may change at high Vin.

    Regards,
    Tim