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MC33063A: Device fails FCC Conducted Emissions Test when designed as a Buck Converter

Part Number: MC33063A

Hi There,

I was wondering if there is any application note or reference design using the MC33063A chip in a buck configuration to regultate 24VDC down to 12VDC.

We we are testing our design, the circuit is failing the conducted emissions test badly for signals below 1MHz.

I have attached an image of our schematic

  • Hello Jason,

    There is an app note for this device, but unfortunately it does not talk about radiated emissions:
    www.ti.com/.../slva252b.pdf

    What do your output switching waveforms look like? Is the inductor having very large current ripple?
    Also potentially a concern is if the device is operating in discontinuous mode of conduction, this can generally cause large ripples when the inductor current goes to 0.

    Best,
    Michael