Article ID: 000075931 Content Type: Troubleshooting Last Reviewed: 09/11/2012

Why do I see a Minimum Pulsewidth Violation on the ALTTEMP_SENSE megafunction?

Environment

  • PLL
  • BUILT IN - ARTICLE INTRO SECOND COMPONENT
    Description

    You may see this error in the Quartus® II software if you use a PLL to derive the input clock frequency to the ALTTEMP_SENSE megafunction.

    The input frequency applied to the internal temperature sensor must be less than or equal to 1.0MHz.  There is a clock divider available in the ALTTEMP_SENSE megafunction to reduce your input clock to meet this requirement. Refer to the Temperature Sensor (ALTTEMP_SENSE) Megafunction User Guide (PDF)  for further details. 

    The rounding nature of the PLL multiply and divide parameters may result in the actual output clock not being exact, and the resulting clock frequency could be higher than the required 1.0MHz if not using the clock divider. If using the clock divider, the resulting clock frequency could be higher than 40.0MHz or 80.0MHz depending on the setting used for the clock divider.

    Resolution To avoid this warning, revise the PLL parameters to make the frequency of the rounded output clock to be less than or equal to 1.0MHz if not using the clock divider.  If using the clock divider, revise the PLL parameters to make the frequency of the rounded output clock to be less than or equal to 40.0MHz or 80.0MHz depending on the setting used for the clock divider.

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