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Original question:

LM5117-Q1: LM5117

LM5117-Q1: TECHNICAL EXPLAINATION REQUIRED FOR SUGGESTED RECOMMENDATION

Sambit Kumar P
Prodigy 40 points
Part Number: LM5117-Q1

Tool/software:

Hello EricLee

Can you please explain the technical reason to me how each of your recommended steps listed below can help in reducing the emissions.

  • Make SW node copper area smaller. 
  • Add RC snubber between the drain and the source of the low-side MOSFET.https://www.ti.com/document-viewer/lit/html/SSZTBC7 
  • Populate a schottky diode in parallel with low-side MOSFET
  • Use shielded inductor with minimized pin lead exposure. The pin leads are hidden on the bottom side in this example. 
  • Locate the 'dot'  (or 'bar') direction of the inductor at the SW node. 
  • 0
    TI__Guru 58481 points

    Hello Sambit 

    • Make SW node copper area smaller. ==> This reduces the coupling between the noisy SW node and earth ground
    • Add RC snubber between the drain and the source of the low-side MOSFET.https://www.ti.com/document-viewer/lit/html/SSZTBC7 ==> This minimizes ringing at SW 
    • Populate a schottky diode in parallel with low-side MOSFET==> This also reduces the ringing at SW node by reducing the reverse recovery charge on the low-side. 
    • Use shielded inductor with minimized pin lead exposure. The pin leads are hidden on the bottom side in this example. ==> It covers noisy SW node with the shield as much as possible. 
    • Locate the 'dot'  (or 'bar') direction of the inductor at the SW node. ==> The 'dot'  indicate the inner side wire of the inductor, which is surrounded by the rest of wires. More shielding effect if the wire is surrounded by the rest of wires.  

    -EL