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Original question:

LM5116: LM5116 Synchronous Buck Converter

LM5116:

umamaheswar peta
Expert 1370 points
Part Number: LM5116
Other Parts Discussed in Thread: PMP7282

Hi,

Initially we have fabricated the PCB using TI PMP7282 reference design gerber file and it is working fine by tuning the input & output Capacitors and also we tuned input(DC 20V to 60V) & output voltage(DC14V) for 50A current.

Then we have gone for the our PCB design and added additional circuit based on the application. In this design, we have not changed the TI PCB layout design,  kept as it is as per TI gerber file and added external circuit to this PCB there was a  minor modification on the power, signal & ground plane to the circuits connected. 

When we fabricated the PCB & assembled  the components and started testing we are facing the issue of the Mosfet gate ringing issue.

The test condition is the input voltage 20V DC , the ringing start at 15A current above and 40V DC input , the ringing starts above 10A current. If we increase the  load/current, the mosfet is failing/shorting, the mosfet fails are from master side top & bottom but more frequent bottom one. 

Please can you suggest or provide support on this issue.

Best Regards,

Umamahesh

  • 0
    TI__Guru 73522 points

    Hi Umamahesh,

    Please send the schematic and layout. In general, the gate parasitic inductance should be minimized - this means running the HO and SW traces as a diff pair to the high-side FET and running LO over a GND plane to the low-side FET. A gate resistor should not be used in series with LO as it adds impedance and may cause Cdv/dt shoot-through as a result of inadequate pull-down when the SW voltage is rising.

    Regards,

    Tim