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DC Sweep of a DFF

canbaltaci

I am making a DC sweep for the CLK input of a DFF. However, I am not able to see the desired clk-to-output (Q) characteristics since I do not know how to set the output value to "1" or "0" at the first sweep value (i.e. the output value of the sim is not a stable operating point at initially).

How can I see the transfer characteristics in such a simulation? Is there a way to set the initial values for DC sweep?

 

Best regards,

Can

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  • You can set the initial condition for a node in the circuit. Search for initial conditions in the spectre manual or whatever simulator you are using.

    However, it doesn't make sense to do it for a DC sweep since DC doesn't simulate the dynamic characteristics of a circuit. I am guessing you are looking for which clock voltage will cause the output to change. You could set the output initial voltage and run a transient simulation with the clock input being supplied with a slow ("nearly DC") voltage ramp. It just needs to be much slower than the clk-to-q time.

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  • You can set the initial condition for a node in the circuit. Search for initial conditions in the spectre manual or whatever simulator you are using.

    However, it doesn't make sense to do it for a DC sweep since DC doesn't simulate the dynamic characteristics of a circuit. I am guessing you are looking for which clock voltage will cause the output to change. You could set the output initial voltage and run a transient simulation with the clock input being supplied with a slow ("nearly DC") voltage ramp. It just needs to be much slower than the clk-to-q time.

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