BQ25798: BQ25798 EMI ISSUE

Charles Lee

Prodigy 10 points

Part Number: BQ25798

Tool/software:

I USE BQ25798 AT INPUT 15V PD AND OUTPUT 2S BATTERY 4A ,HAVE EMI ISSUE at 90MHZ , 330Mhz ,have any method can solve.

ic frequency 750khz, sw1,sw2 have snub 1 ohm+ 2.2n ,I need under 6dB

,thank you.

29 days ago

0 Jeff F 27 days ago

TI__Guru**** 152756 points

Hi Charles,

Tuning the snubbing R and C is an empirical process. Please review the appnote at the link below:

https://www.ti.com/lit/an/slva255/slva255.pdf.

You will need an oscope with > 330MHz bandwidth and a tip and barrel scope probe to measure the SWx node switching frequency.

Regards,

Jeff

0 Charles Lee 26 days ago in reply to Jeff F

Prodigy 10 points

sw wave

0 Jeff F 26 days ago in reply to Charles Lee

TI__Guru**** 152756 points

HI Charles,

Is BW limit turned on for CH1? I don't see any ringing.

Regards,

Jeff

0 Charles Lee 25 days ago in reply to Jeff F

Prodigy 10 points

Dear Jeff

I expanded the waveform and used full bandwidth. In addition to RC, which side can be adjusted.

0 Jeff F 25 days ago in reply to Charles Lee

TI__Guru**** 152756 points

Hi Charles,

If you follow the steps in https://www.ti.com/lit/an/slva255/slva255.pdf, you can optimize the snubber for the get rid of the ringing on the falling edge. That might be the cause of the EVM.

Regards,

Jeff

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BQ25798: BQ25798 EMI ISSUE