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USB hosts hubs transceivers Forum Discussions

MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Dear Sirs and Madams,

 

We were introduced to the SiT which is a transmitter that meets the needs of the HX2VL.

Please refer to the solution at the URL below.

 

https://community.cypress.com/t5/USB-Hosts-Hubs-Transceivers/CY7C65642-Rise-time-fall-time-specifica...

 

When We measured the RMS Jitter of SiT8008,
The measured value was 589.4 [ps] at BW 10-5MHz.

 

SiT8008 BW10-5MHz.png

 

 

 

 

 

 

 

 

 

 

 

 

 

According to Cypress application note AN72332
Jitter (RMS): 260 [ps (Max)]

It seems that the above specifications are not met, is that okay?

Could you comment about this result?

 

Regards,

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1 Solution
Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

Sorry for the delay in response. I confirmed that we use the filtered jitter mask for HX2VL clock specification so you could use the measured RMS phase jitter value in the 12 kHz to 5 MHz range. Since that meets the RMS phase jitter requirements in the App Note, you could use this oscillator part for the board.

Best Regards,
Sananya

View solution in original post

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8 Replies
MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

The part number under consideration is "SiT8008BC-13-33S-12.000000".

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Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

We checked the datasheet and this part look okay in terms of the spec. Please refer to the test report from crystal webpage to check if this could be a measurement error.

Please also verify the power supply ripple as it should be very low. To reduce the crystal jitter, the VDDD decoupling should be 0.1uF or even less.

Best Regards,
Sananya

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MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Sananya-san,

We try to confirm the possibility of error due to the measurement path.

Do you know if SiT8008BC has been used as an oscillator for CY7C65642 ( or HX2LP series)?

 

Regards,

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Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

No, we havent tested with this particular oscillator since our DVKs are based on the 12MHz crystal.

Best Regards,

Sananya

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MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Sananya-san,

 

After all, it may be necessary to discuss the BW of the clock.

 

The BW of the waveform sent earlier is 10 Hz to 5 MHz and the RMS phase jitter characteristic is 589 ps.

With the same waveform and a BW of 12 kHz to 5 MHz, the RMS phase jitter is 2.89ps.

SiT8008 BW12k-5MHz.png

In the BW range from 10kHz to 5 MHz, the RMS phase jitter characteristics are close to the SiT data sheet specifications.

キャプチャ.PNG

Cypress said it doesn't have any information about BW, but does this phase characteristic below 12kHz affect the internal PLL of the HX2LP?
Please could you tell us the reason?

 

Regards,

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Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

Sorry for the delay in response. I confirmed that we use the filtered jitter mask for HX2VL clock specification so you could use the measured RMS phase jitter value in the 12 kHz to 5 MHz range. Since that meets the RMS phase jitter requirements in the App Note, you could use this oscillator part for the board.

Best Regards,
Sananya

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MaMi_1205306
Level 7
Level 7
500 replies posted 50 solutions authored 25 likes received

Hi, Sananya

Your comments give us peace of mind when using the SiT8008.

However, it may be better to specify the frequency band in the specifications of HX2VL's Jitter RMS.

Reagrds,

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Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hello,

Yes, I will provide the feedback and check internally if we can update the App Note with frequency band specifications for RMS jitter.

Best Regards,
Sananya

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