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.

10 months ago

0 Jeff F 10 months ago

TI__Guru**** 166136 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 10 months ago in reply to Jeff F

Prodigy 10 points

sw wave

0 Jeff F 10 months ago in reply to Charles Lee

TI__Guru**** 166136 points

HI Charles,

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

Regards,

Jeff

0 Charles Lee 10 months 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 10 months ago in reply to Charles Lee

TI__Guru**** 166136 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

Power management

Power management forum

BQ25798: BQ25798 EMI ISSUE