LM5085: Test radiation overshoot

Timsen

Part Number: LM5085

Dear all；

I'm using LM5085, output 9V.When testing the radiation, it was found to exceed the standard. The following is the schematic diagram and PCB Layout. Please help to check, Any Suggestions for reducing radiation?

Thank you！

over 4 years ago

0 Iven Su over 4 years ago

TI__Expert 8245 points

Hi,

How is your load and at which frequency you found it exceed the standard? On the layout, I think the second and third layers should be copper covered.

0 Timsen over 4 years ago in reply to Iven Su

Expert 1660 points

Dear Iven：

1，The load is around 1A

2，The radiation was about 2DB above the limit

3，The following is the updated layout

0 Iven Su over 4 years ago in reply to Timsen

TI__Expert 8245 points

Hi,

I think this time should be better. You can also put a gate resistor (less than 10Ohm) to control the slew rate of MOSFET switching, it also helps on the radiated EMI.

0 Timsen over 4 years ago in reply to Iven Su

Expert 1660 points

Dear Iven：

“put a gate resistor (less than 10Ohm) to control the slew rate of MOSFET switching”, Where is the 10Ω resistance added? Can you give me a schematic diagram?

Thank you!

0 Iven Su over 4 years ago in reply to Timsen

TI__Expert 8245 points

Hi,

The resistor should be put between U83 Pin6 and D822 Pin1.

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LM5085: Test radiation overshoot