MC33063A: CE Test Failing

Gopala Krishna1

Prodigy 50 points

Part Number: MC33063A

Hi,

In one of our application, using MC33063A in buck configuration to convert 24V DC to 5V DC.

Part of EMI/EMC testing, this circuit is failing CE and RE test at 13.8MHz

I have attached our application schematic.

Please suggest me a solution

over 3 years ago

0 Brigitte over 3 years ago

TI__Guru 58225 points

Hello Gopala,

Would you please re-attach your schematic? It seems there was an issue.

0 Gopala Krishna1 over 3 years ago in reply to Brigitte

Prodigy 50 points

Hi Ma'am

Here is the schematic application circuit.

0 Gopala Krishna1 over 3 years ago in reply to Brigitte

Prodigy 50 points

Sch Attached.docx

0 Brigitte over 3 years ago in reply to Gopala Krishna1

TI__Guru 58225 points

Hello Gopala,

RE and CE means radiated and conducted emission, is this correct?

Could you please send a measurement of the switch node with a 500 MHz scope and probe (at least) with 100ns per division and then the rising and falling edge?

The rise and fall time of the switch node might emit at this high frequency and then if C5 is very close connected to the inductor and power GND, it might be possible to be used as filter. But you need to select a capacitor that is still capacitive at this frequency. 100nF are about to get inductive at this frequency, so replacing with a 10nF cap might help.

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MC33063A: CE Test Failing