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Boon-Siang Cheah

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Custom Circuit
Design Engineer

Posts: 14
Essex Junction, VT

How to plot sawtooth in SpectreMDL?
Apr 18^th, 2007, 2:36pm

Hi,
Does anybody know how to create a sawtooth waveform with SpectreMDL? I am trying to simulate receiver hysteresis noise immunities by injecting a noise pulse at the switchpoints. I would like to inject the pulse at the receiver input as shown in the attached file. Please comment or give me some suggestions on how to do this in SpectreMDL? If I have to, I can also do this in ADE.

Thank you very much.

Cordially,
Boon-Siang

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DesignerGuidePosting.pdf

Cordially,
Boon-Siang Cheah
Circuit Design Engineer

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Ken Kundert Global Moderator Offline Posts: 2386 Silicon Valley	Re: How to plot sawtooth in SpectreMDL? Reply #1 - Apr 18^th, 2007, 3:21pm I would recommend using Verilog-A to generate the sawtooth waveform, and then simulate the whole thing with MDL. Alternatively, you can use a PWL waveform with the conventional sources (vsource, isource, port) to produce a sawtooth. -Ken
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Boon-Siang Cheah

Junior Member

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Custom Circuit
Design Engineer

Posts: 14
Essex Junction, VT

Re: How to plot sawtooth in SpectreMDL?
Reply #2 - Apr 19^th, 2007, 1:31pm

Hi Ken,

Thank you very much for the reply. I think you might have misunderstood what I wanted to do. I'm not trying to setup a circuit to create sawtooth waveform generator circuit. I am trying to create an input waveform like the previous posting attachment. I am trying to create input waveform with noise pulse (with different amplitude if possible) to determine my receiver hysteresis immunities. The attachment waveform was created with one of our in house spice simulator. I would like to know if there's a way I can replicate the same input with SpectreMDL/Spectre/Ultrasim.

Thank you very much.

Boon-Siang

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Cordially,
Boon-Siang Cheah
Circuit Design Engineer

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Ken Kundert Global Moderator Offline Posts: 2386 Silicon Valley	Re: How to plot sawtooth in SpectreMDL? Reply #3 - Apr 20^th, 2007, 9:44am Yes, I understood what you are asking for. You can use either Verilog-A or a piecewise linear source to produce your stimulus waveform. -Ken
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Boon-Siang Cheah

Junior Member

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Custom Circuit
Design Engineer

Posts: 14
Essex Junction, VT

Re: How to plot sawtooth in SpectreMDL?
Reply #4 - Apr 20^th, 2007, 12:06pm

Hi Ken,

I know how to use PWL to generate the pulse but it's quite cumbersome because I would like to change the amplitude of the pulse. Could you give me some examples on how to do it with VerilogA? Or advice me on what references to look at?

Thank you very much for your help. I really appreaciate it.

Boon-Siang

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Cordially,
Boon-Siang Cheah
Circuit Design Engineer

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Ken Kundert

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Silicon Valley

Re: How to plot sawtooth in SpectreMDL?
Reply #5 - Apr 20^th, 2007, 2:50pm

If you are using Spectre, you can use the scale parameter on the PWL source to adjust the waveform amplitude. If you instead want to use Verilog-A, there are a lot of different ways of doing it, and the best way will depend strongly on the details of the waveform. I'm afraid I'm not going to be able to help you with that other than suggest you learn the language by picking up a copy of my book or by studying the examples on verilog-ams.com, or both. It is definitely worthwhile taking the time to learn it.

-Ken

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