DS90UB953-Q1: How can I suppress EMI at 1.6 GHz and 2 GHz?

YOSHIAKI NAKAMICHI

Prodigy 30 points

Part Number: DS90UB953-Q1
Other Parts Discussed in Thread: DS90UB960-Q1, ,

Hello,

I operated DS90UB953-Q1 in Synchronous mode, and REFCLK of DS90UB960-Q1 is inputting 25 MHz.

At this time, I observed EMI at 1.6 GHz and 2 GHz from the coaxial cable.

Please tell me how to suppress this EMI.

Regards,

over 7 years ago

0 Palaniappan Manickam over 7 years ago

TI__Genius 10475 points

Hello,
Please refer to these other recent E2E threads on this same topic:
e2e.ti.com/.../700194
e2e.ti.com/.../700485

One option is to use the non-synchronous internal clock mode (953 uses the internal clock so no external oscillator is needed) to reduce the spurs. This new mode is being added to the 953 datasheet which is currently undergoing a revision. So more information on this mode will be available soon.
Another option is to use the spread spectrum option on the 960 REFCLK. This will be available in the 960 datasheet.

0 YOSHIAKI NAKAMICHI over 7 years ago in reply to Palaniappan Manickam

Prodigy 30 points

Hello,

Thank you very much.
I understood about countermeasures.
Why does EMI occur at 1.6 GHz and 2 GHz at REFCLK = 25 MHz, please tell me the principle.

Regards,

0 Liam Keese over 7 years ago in reply to YOSHIAKI NAKAMICHI

TI__Genius 12705 points

Hello,
EMI performance is a system level parameter that involves many aspects PCB layout and grounding as well as clock and frequency planning. Without in depth analysis it is difficult to predict, however CSI-2 frequency is often specified at 1.6Gbps rate.
We have added the described clocking mode options for providing some additional noise margin to help mitigate any observed issues to existing designs.

Regards,

0 YOSHIAKI NAKAMICHI over 7 years ago in reply to Liam Keese

Prodigy 30 points

Hello,
We observed 1.6 GHz with DS90UB953-Q1EVM.
Please confirm the phenomenon confirmation and cause analysis with DS90UB953-Q1EVM and tell us the result.
We will consider the proposed countermeasures.

Regards,

0 Liam Keese over 7 years ago in reply to YOSHIAKI NAKAMICHI

TI__Genius 12705 points

Hello,
It is difficult to determine cause without sharing measurement data/ conditions etc. I have sent request for exchange of information offline.
For mitigation in synchronous mode the most robust is to have SSC applied at REFCLK input to the 960 as this will provide spread spectrum to all system frequencies.

Interface

Interface forum

DS90UB953-Q1: How can I suppress EMI at 1.6 GHz and 2 GHz?