DP83TG720S-Q1: How much SGMII Clock setup when DP83TG720SWRHARQ1 wotk with 1000Mbps?

Hello,

I do not understand your question. What do you mean by how much clock setup? Could you please rephrase?

Sincerely,

Georme

Dear 

Thanks very much for your reply!

I want to konw the work frequency of SGMII.

When we use Signal Analyzer scan  DP83TG720SWRHARQ1 on board, 1562MHz is very high.

So, I'm sure it's due to the SGMII signal. 

Could you to provide a way to reduce the radiated energy. Such as: Spread spectrum or Change frequency or others.

Thanks!

Wang Yuxue

Hi,

SGMII standard defines the signal to be 625MHz. How sure are you that this is due to SGMII? Can you try disabling SGMII on PHY and seeing if spur is still present?

Unfortunately, there are no software fixes for this available. The only option to improve would be improve board layout.

Sincerely,

Gerome

Dear Gerome

Thanks very much for your reply!

I am confirmed again, and have new find.

Signal Analyzer scan result as bellow, from the frequency point, about 62.5MHz is real cause.

When i power down DP83TG720S-Q1, the Peak point disappear immediately！

So, Please help comfirm DP83TG720S-Q1 work states, what cause of radiation.

We use DRA821 connect this PHY, whether we can open SSC Function?

Thanks!

Wang Yuxue

Hi Wang,

Please allow me to get back to the team regarding this information. Can you confirm that this is due to SGMII? If you disable SGMII, but keep PHY on, are you still able to see these spurs?

Sincerely,

Gerome

Hi,  Gerome 

When i disable SGMII, those spurs disappers.

Thanks

Wang Yuxue

Hello Wang,

Can you please provide the register settings for disabling SGMII? In addition, is CLKOUT active? If so, please disable it and see if it has effect on spurs.

Sincerely,

Gerome

Hi,  Gerome 

CLKOUT has been disabled, but the spurs also exist. 

We try enable CLKOUT, more spurs appear, such as 1550MHz, 1600MHz.

Thanks

Wang Yuxue

Hi, Gerome

Can you help explain how to judge the influence of layout? 

The section 7.4.8.2 is not layout guide?

Wang Yuxue