Driving CX3 clocks using Si5351A

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StuartTyler
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First reply posted First question asked Welcome!

Hello, I am designing a MIPI to USB3SS interface with the CX3 CYUSB3065-BZXC. The CX3 needs 3 clocks (to use watch dog). The MIPI sensor we are using uses a 37.125MHz clock, and so expecting that this will feed into REFCLK. Also a 19.2MHz clock is needed, and the 32kHz clock. I am thinking of using the Si5351A-B-GT with a single xtal to generate these 3 clocks, but concerned about the phase noise spec requirement on the CX3. Will the Si5351A and a crystal meet the CX3 phase noise requirement?

Here is the Si5351A jitter spec of 155ps pk-pk worst case.

StuartTyler_1-1668638555049.png

And the CX3 phase noise spec.

StuartTyler_0-1668638515908.png

Im not too sure how to reconcile if this part is okay to use or not.

It would be nice, as a single xtal can be used and then the output frequencies changed easily on a design.

Help on understanding if the Si5351A is suitable or not with the CX3 is appreciated.

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1 Solution

Hello,

I came across lower jitter parts, like the Si5332. The jitter spec is typ 12ps pk-pk. Looks like this part is sensible. Anyone used the Si5332 with the CX3?

>> Unfortunately, we do not use this part number in our reference designs. You can refer to CX3's reference designs and we recommend to use the part numbers which meet the clock requirements in the CX3 datasheet.

 

Regards,
Rashi

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2 Replies
StuartTyler
Level 1
Level 1
First reply posted First question asked Welcome!

Plugging the phase noise profile into: https://rf-tools.com/jitter/

Gives: RMS Phase Jitter in seconds: 4.268 ps. Converting to pk-pk is an estimate multiplier. If you like using x6 or x10. Any way up, that 42ps pk-pk, and the Si5351A spec of 150ps is way too noisy. My guess is a factor of 3. 

I came across lower jitter parts, like the Si5332. The jitter spec is typ 12ps pk-pk. Looks like this part is sensible. Anyone used the Si5332 with the CX3?

0 Likes

Hello,

I came across lower jitter parts, like the Si5332. The jitter spec is typ 12ps pk-pk. Looks like this part is sensible. Anyone used the Si5332 with the CX3?

>> Unfortunately, we do not use this part number in our reference designs. You can refer to CX3's reference designs and we recommend to use the part numbers which meet the clock requirements in the CX3 datasheet.

 

Regards,
Rashi
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