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I trying to make tps54202 switch regulator for esp32-wroom which would pass EMC test. https://www.ti.com/tool/TIDA-00948 By reading guidelines of designing they say that to pass EMC test you need to add small filter L+C of 5uH and 10uF. However they dont provide this filter layout, schematic or BOM. I can figure out schematics and pcb layout, but not BOM for input filter, as there are many complicated formulas to calculate esr value, resistance, etc... Anyone could reccomend me BOM for input filter?

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Choose a ceramic capacitor with an X7R temperature coefficient and a voltage rating of at least 25 volts, and an inductor with at least a 1 amp rating at 125 Celsius. The schematic is

schematic

simulate this circuit – Schematic created using CircuitLab

Keep the traces as short and wide as possible, and run the ground trace from C7-ground directly to the ground of input capacitors C5 and C2 (also short as possible). Run the Trace from L2 directly to the high side of input capacitors C5 and C2.

Good Luck!

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  • \$\begingroup\$ Should L2 be ferrite based? And what aprox esr resistance C7 should be? \$\endgroup\$ – TheAfrizzz Jan 24 at 21:05
  • \$\begingroup\$ L2 should be a shielded power inductor and will have a ferrite core, and any multilayer ceramic cap with an X7R rating will have a low enough ESR. There won't be too much current in the cap anyway; this circuit is just to filter the switching noise from getting back onto the line input. \$\endgroup\$ – John Birckhead Jan 24 at 23:34
  • \$\begingroup\$ Thanks you are the best! \$\endgroup\$ – TheAfrizzz Jan 25 at 0:31

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