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altera_pll Fractional-N PLL error using physical output clock parameters

HypeInst
New Contributor I
186 Views

I receive the following error message when attempting to configure the altera_pll MegaCore in Fractional-N mode using physical output clock parameters:

"The specified configuration causes Voltage-Controlled Oscillator (VCO) to go beyond the limit." 

My chosen parameters should not be problematic.  Please see the attached screenshot.

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1 Solution
Ash_R_Intel
Employee
171 Views

The Fvco achieved by the settings that you had made is beyond the limit specified in the datasheet. For Arria V, Stratix V and Cyclone V device the Fvco min = 600 MHz.

Best way is to first enter the 'Desired Frequency' and let the tool calculate the parameters. You may then adjust the values if more refinement is required.


Please refer, Altera PLL IP Core User Guide, https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/altera_pll.pdf and AN 661, https://www.intel.com/content/www/us/en/programmable/documentation/mcn1424769382940.html for more details.


Regards.


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3 Replies
Ash_R_Intel
Employee
174 Views

Hi,


What is the output frequency that you are trying to achieve?


Regards.


Ash_R_Intel
Employee
172 Views

The Fvco achieved by the settings that you had made is beyond the limit specified in the datasheet. For Arria V, Stratix V and Cyclone V device the Fvco min = 600 MHz.

Best way is to first enter the 'Desired Frequency' and let the tool calculate the parameters. You may then adjust the values if more refinement is required.


Please refer, Altera PLL IP Core User Guide, https://www.intel.com/content/dam/www/programmable/us/en/pdfs/literature/ug/altera_pll.pdf and AN 661, https://www.intel.com/content/www/us/en/programmable/documentation/mcn1424769382940.html for more details.


Regards.


HypeInst
New Contributor I
157 Views

Thank you for your response!  I'm sorry that I previously missed the Fvco limitations.  I see those in the datasheet now and will revise accordingly.  Thanks again!

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