DS90UB954-Q1: How to reduce EMI noise?

NOBUO FUJIHARA

Genius 9335 points

Part Number: DS90UB954-Q1

Hi Manickam-san,

My customer is also suffered from radiated EMI with 953/954 system.

Q.1) What kind of side effect expected to apply non-sysnc mode instead of REFCLKL of 954 in actual use in applicatoin?

Is this recommended mainly for EMI measurement use case?

Q.2) Additionally, my customer also see radiation from Dout- port with PoC single-ended configuration.

Do you expect any drawback if customer put beads on Dout- line?

Regards,

Nobuo Fujihara

over 7 years ago

0 Palaniappan Manickam over 7 years ago

TI__Genius 10475 points

Fujihara-san,
There shouldn't be any downside when using the internal clock mode to reduce the spurs for EMI. This 953 non-synchronous internal clock mode has now been validated and is being added to the 953 datasheet currently under revision.
Also the spread spectrum for 954 REFCLK is an option to improve the EMI performance and this is being added to the 954 datasheet based on our validation.

0 NOBUO FUJIHARA over 7 years ago in reply to Palaniappan Manickam

TI__Genius 9335 points

Manickam-san,
I understood no drawback to use 953 internal clock mode.
Could you also advice if it's effective putting beads on "Dout-" port to reduce radiated EMI in single ended use case?
I expect putting beads on "Dout-" improve EMI a little, but will it make any negative concerns like degrade transmission quality?

Best regards,

0 NOBUO FUJIHARA over 7 years ago in reply to NOBUO FUJIHARA

TI__Genius 9335 points

Hello,
Is there any concern to put ferrite beads on Dout- port to supress radiated emmission, like increasing mismach between Dout+ ?
Regards,

0 Liam Keese over 7 years ago in reply to NOBUO FUJIHARA

TI__Genius 12705 points

Placing ferrite beads on the Dout is not recommended as it will greatly affect the channel characteristics of the RF path.

Regards,

0 NOBUO FUJIHARA over 7 years ago in reply to Liam Keese

TI__Genius 9335 points

Does it also affect to RF path when putting ferrite beads on DOUT- port with single ended configuration?
Regards,

0 Liam Keese over 7 years ago in reply to NOBUO FUJIHARA

TI__Genius 12705 points

Yes, this also can affect the signal path. The output impedance seen at the DOUT- should match close as possible to what is at DOUT+

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DS90UB954-Q1: How to reduce EMI noise?