BQ25890: EMI Recommendation Document

Daniel Rahardja

Part Number: BQ25890

Hi,

I am trying to solve radiated EMI problem with our charger design using BQ25890. I found this recommendation document https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/bq2589xbq2419x_5F00_29xlayoutandEMIrecommendation.pdf

On page 11 it is mentioning about "BQ241xx EMI Consideration" document. Could I get access to this document?

Thanks.

over 6 years ago

0 Jeff F over 6 years ago

TI__Guru**** 166826 points

Hi Daniel,

I apologize but I am not aware of this document. If you have specific questions, I would be happy to answer them.

0 Jeff F over 6 years ago in reply to Jeff F

TI__Guru**** 166826 points

Daniel,

Do you have any EMI questions that I can answer for you?

0 Daniel Rahardja over 6 years ago in reply to Jeff F

Prodigy 30 points

Jeff,

After implementing below,

RC snubber at Vsw node

Value: (1R3-S3A-0.5W) + (820pF-S2X-50V)

1nF Bypass: PMID, VBUS, VSYS

BTST: 10 ohms

VBUS Ferrite Bead: 120ohms, 0805

I can see much improvement compare to the original.

I will do another EMI pre-scan in the next couple of weeks to verify if the mitigation is enough to pass FCC class B limit.

Do you have any other suggestion for improvement?

Thanks.

0 Jeff F over 6 years ago in reply to Daniel Rahardja

TI__Guru**** 166826 points

Great! A snubber will always reduce EMI but at the expense of efficiency. First option is a small 0.01-0.1uF capacitor as close to PMID and GND as possible. If that doesn't work then you can try slowing down the FET turn on/off times with a resistor in series with BTST capacitor but you will also see an efficiency hit.

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BQ25890: EMI Recommendation Document