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USB Hosts Hubs Transceivers

MaMi_1205306
Honored Contributor

Dear Sirs and Madams,

 

The item "Table 3. External Clock Input Requirements" is defined in AN72332, where "Rise time / fall time 3 [ns] (Max)" is specified. 

Please tell us this voltage condition. (For example, 20% -80% VCC, not specified, etc.)

AN72332

https://www.cypress.com/file/122726/download

 

Regards,

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1 Solution
Sananya_14
Moderator
Moderator

Hello,

 

The voltage level is from 10%-90% VCC for the rise/fall time specification in AN72332. As you mentioned, the KYOCERA KC2520K 12.0000 C10E has a maximum rise time of 4.5ns which is greater than 3ns. This could work with HX2VL but we recommend checking other oscillators that meet the specification such as SiT1602/SiT8008.

 

Best Regards,

Sananya

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MaMi_1205306
Honored Contributor

We are currently selecting a crystal oscillator.

Current product

EPSON SG-210SCB 12.000MHz

Rise time / Fall time : 3 ns (Max) 20% VCC to 80% VCC

 

The current crystal oscillator could be used without any problem, but it became difficult to obtain it, and we are considering changing parts.

 

Modified product KYOCERA KC2520K 12.0000 C10E (12.000MHz)

 

However, this crystal oscillator has a "Rise time / Fall time of 4.5 ns (Max) 10% to 90% Output Level" as specified in the data sheet.

We think the conditions in this voltage range are important.

Therefore, please tell us about the XIN conditions for HX2.

 

Regards,

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Sananya_14
Moderator
Moderator

Hello,

 

The voltage level is from 10%-90% VCC for the rise/fall time specification in AN72332. As you mentioned, the KYOCERA KC2520K 12.0000 C10E has a maximum rise time of 4.5ns which is greater than 3ns. This could work with HX2VL but we recommend checking other oscillators that meet the specification such as SiT1602/SiT8008.

 

Best Regards,

Sananya

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MaMi_1205306
Honored Contributor

Sananya-san,

 

Thank you for your infomation.

We will try to find an alternative product by referring to the information you received.

However,  If 3.5ns has a spec of 10%-90%, it is highly possible that the Epson product you are currently using does not meet the conditions.

EPSON SG-210SCB 12.000MHz

Rise time / Fall time: 3 ns (Max) 20% VCC to 80% VCC

 

Please describe the conditions for this 3.5ns in this application note.

 

Regards,

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Sananya_14
Moderator
Moderator

Hello,

Could you please let me know the reference to the EPSON SG-210SCB product in our App Note?

As per the maximum rise time value of 3ns in Table 3, the rise time calculation is for 10% to 90% VCC but doesn't mention any specific external oscillator that we used with HX2VL.

Best Regards,

Sananya

 

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MaMi_1205306
Honored Contributor

Sananya-san,

 

Regarding the external clock of the application note, the slew rate is described only for 3ns, and I think that there is no description of 10% to 90% of VCC.

We chose Epson SG-210SCB with a maximum value of 3ns, but the specified is 20% to 80% of VCC.

I thought that if the maximum value of 3ns according to this application note is 10% to 90%, it will exceed the maximum value of 3ns.

Therefore, I think it is better to have a description of 10% to 90% in the slew rate specifications of the application note.

 

Regards,

 

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Sananya_14
Moderator
Moderator

Hello,

 

Yes, I understand your point. It may be that the description was not added since most datasheets have rise time for 10% to 90% VCC. Since the Epson oscillator exceeds the 3ns maximum limit marginally, it may have caused no issues in the HX2VL working.

I will check internally if we could update the description in the App Note.

 

Best Regards,

Sananya

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