BQ25120F3A: Conductive Emission test (FCC part 15C) fails

PSG_4

Part Number: BQ25120F3A

Tool/software:

Hi ,

When we are doing pre compliance test (FCC part 15C),it is noted that Conductive Emission test failed at both Line as well as Neutral at 307.5KHz as well as 620KHz ( second harmonic) .

It seems BQ25120F3A buck power supply inductor switching (1.8V SYS power) is causing the issue. Do you have any suggestions to reduce CE emissions because of BQ25120F3A ?

Regards

PSG_4

3 months ago

0 PSG_4 3 months ago

Intellectual 610 points

TEST_02_CE WITH BLE 2_44_6dB_150kHz to 30 MHz Line.docx

0 Juan Ospina 3 months ago in reply to PSG_4

TI__Genius 14885 points

Hi,

Reducing CE emissions can be handled in a few ways. Board layout can have significant impact on EMI, if you have a board layout to share I can maybe give tips on this, but the primary recommendation would be reducing the size of the buck current loop and ensuring components are as close to the IC as possible.

Additionally a snubber circuit can help to reduce ringing noise and have an impact on EMI as well. You can also reference some of our online documentation on reducing switching noise.

Best Regards,

Juan Ospina

0 PSG_4 2 months ago in reply to Juan Ospina

Intellectual 610 points

Hi,

Sorry for late reply. Attached the layout of BQ24120F3A with marking of inductor L,Cin, and Cout.

Let me know the recommended values of Snubber circuit values . Also Ferrite bead part number /properties.

-PSG_4

0 Wyatt Keller 2 months ago in reply to PSG_4

TI__Guru** 104905 points

Hello,

The references in the technical article Juan had shared shows some methods to estimate the R-C values for the snubber: https://www.ti.com/lit/pdf/ssztbc7

Sincerely,

Wyatt Keller

Power management

Power management forum

BQ25120F3A: Conductive Emission test (FCC part 15C) fails