I am working on Delay Locked loop Project. I want to check the lock range of the dll. I am using vpulse for clock but by giving parameters clock period, clock width, rising time, falling time. It giving the clock pulse with same frequency.

I want the variable clock frequency. Is there another type of clock source which give me the variable clock frequency.

I am using Cadence Virtuoso tool and i am doing project in GPDK 180nm technology.

Anyone please help me to solve this problem.

  • 1
    \$\begingroup\$ You have posted the same question twice, please delete one of them. \$\endgroup\$
    – alexan_e
    Commented Apr 5, 2014 at 6:53

1 Answer 1


The best way is probably to make the clock period of your vpulse source a variable (let's call it clkPer), and the width equal to 0.5*clkPer. Then run a parametric analysis with clkPer as the varied parameter. Plot the output of your DLL and you can see if it has locked or not at each clock frequency.

  • \$\begingroup\$ I have done the parametric analysis but is gives the different graph for differ clock period.....I want variable clock frequency in single pulse.... \$\endgroup\$ Commented Apr 7, 2014 at 7:26
  • \$\begingroup\$ I'm not sure what you mean by 'variable clock frequency in a single pulse'. A single pulse can only have one frequency. Can you elaborate? Getting multiple graphs is what I would expect from the parametric sim. What you could try is using the built in calculator to set a measurement of DLL output frequency as one of the simulation outputs. When you run the parametric, it should measure it every time and plot it against the swept input parameter (clkPer) for you. That should show the range that the DLL locks over. \$\endgroup\$
    – sobremesa
    Commented Apr 7, 2014 at 20:40
  • \$\begingroup\$ I think @user3244121 wants to observe the transient response when the loop is locked and there is a change in input frequency i.e., how the PLL tracks input frequency when there is say a step change in input frequency. \$\endgroup\$
    – JGalt
    Commented Sep 29, 2016 at 12:15

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