CDCM6208V1EVM: We used a spectrometer to test the spectral characteristics of the output at 40MHz, and it was obvious that there was spurs at the proximal edge of the spectrum.

aiwen chen

Part Number: CDCM6208V1EVM
Other Parts Discussed in Thread: CDCLVC1104, CDCM6208

This is schematic diagram.

The clock comes from "a constant temperature crystal oscillator + clock buffer chip", the constant temperature crystal oscillator is Taiwan Taiyi's constant temperature crystal oscillator OCXO, and the clock buffer chip is silicon's Si53301 (1U device form) or TI's CDCLVC1104 (portable device form)

This is the basic configuration。

In this image, we tested the 40MHz spectral characteristics of its output with a spectrometer, and it is obvious that there is spur at the proximal edge of the spectrum.The 10MHz reference clock is still very clean, we have measured it.
So what is the cause of edge spurs and what is the solution.

over 1 year ago

0 Noel Fung over 1 year ago

TI__Guru* 81670 points

Hi Aiwen,

Can you send use the plot again with Center = 40.2MHz and Span=500kHz? Ref should be set to 0dBm or 10dBm.

0 aiwen chen over 1 year ago in reply to Noel Fung

Intellectual 625 points

Hi Noel

Thanks for you reply

It's strange that we have this problem this time. We have a total of three main control boards with business boards containing CDCM6208. Two of the main control boards are ok and one is the main control NO OK. The clock scheme of nok's main control board is a constant temperature crystal + clock buffer (SI53301), and the clock scheme of the main control board of ok is a constant temperature crystal oscillator directly output 10MHz or a constant temperature crystal + clock buffer (cdclvc1104). Is Silicon Corporation's buffer not working with TI's PLL?

0 Noel Fung over 1 year ago in reply to aiwen chen

TI__Guru* 81670 points

Hi Aiwen,

I think this is more or less an application issue, maybe the schematic is not correct with Si53301.

0 aiwen chen over 1 year ago in reply to Noel Fung

Intellectual 625 points

Hi Noel；

Please Help to check the schematic , I don't know if there's a problem with the schematic。Thanks!

0 vicente flores prado over 1 year ago in reply to aiwen chen

TI__Genius 12961 points

Hi Aiwen,
I think we have two separate threads...
Has the issue been resolved? In the other thread the latest response was that the issue has been resolved and the issue was with the Si buffer?

Regards,

Vicente

0 aiwen chen over 1 year ago in reply to vicente flores prado

Intellectual 625 points

Hi vicente;

Thanks for your reply,

Until now, I didn't know the cause of the problem, and the cause of the previous problem was just my own guess, so I would like to ask if there is any good advice，Is it the schematic design or something else？Could you please help to check it.

0 vicente flores prado over 1 year ago in reply to aiwen chen

TI__Genius 12961 points

Hi Aiwen,
I am not familiar with Si buffers, but I do remember this issue being seen only with the Si buffer. If the issue is with the Si buffer, I propose changing it. TI has buffer's that can replace this faulty component

Regards,

Vicente

0 aiwen chen over 1 year ago in reply to vicente flores prado

Intellectual 625 points

Hi vicente；

thanks，Could you please recommend TI's buffer to replace this faulty component?

0 vicente flores prado over 1 year ago in reply to aiwen chen

TI__Genius 12961 points

Hi Aiwen,
I see this is a 2:6 buffer.
What input format are you using and how many outputs are needed and the output formats?
In the schematic I see one SE outputs and one differential output.

Regards,

Vicente

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CDCM6208V1EVM: We used a spectrometer to test the spectral characteristics of the output at 40MHz, and it was obvious that there was spurs at the proximal edge of the spectrum.