PULSE waveform with number of cycles

[shubha-awasthi]

Hello,

I would like to request the inclusion of a pulse waveform that specifies the number of cycles. If there is an alternative approach to handling this in the current version, I would greatly appreciate any guidance.

Looking forward to your response.

Best regards,
Shubha

[marcin-golebiowski]

@shubha-awasthi I think this would need to be addressed in core Spice# library.
@svenboulanger Is there any chance to add it soon to the library?

[svenboulanger]

Hi, I did a quick scan in other SPICE documentation and it seems to me that the REPEAT parameter typically refers to the period (in seconds) of a PWL waveform. I'm not sure if this is what the request is about.

You mentioned a number of "cycles". Does that mean you want to specify a number of pulses/repeats when you use the PULSE waveform? In traditional SPICE this is usually done by building a PWL waveform with the number of pulses you need.

[shubha-awasthi]

sorry to confuse you with that. I actually looked at the LTSpice documentation https://www.analog.com/en/resources/technical-articles/ltspice-piecewise-linear-functions-for-voltage-current-sources.html

Repeating data pairs a specified number of cycles, or forever:
PWL REPEAT FOR 5 (0 0 1m 1 2m 1 3m 0) ENDREPEAT
PWL REPEAT FOREVER (0 0 1m 1 2m 1 3m 0) ENDREPEAT

You’re correct—it refers to the number of cycles. I’ve been using a text file to define a specific count, such as 10 pulses, for this purpose.

[shubha-awasthi]

Hello again, Will it be possible to integrate "Trigger" as well? :)

[svenboulanger]

Thanks for the clarification. I was looking in the wrong direction. I found the full description here: LTSpice Wiki, showing that there is more going on than a simple repeat. LTSpice allows nesting and concatenating waveform definitions, so providing a "general" core implementation I don't think is useful here.

Perhaps the PWL waveform should be modified to work using an interface that can provide the points of the PWL dynamically. Then @marcin-golebiowski can parse those REPEAT statements into a class that implements that interface. I can't really see a cleaner way to deal with nested repeats, concatenated waveforms and forever-repeating waveforms.

The TRIGGER behavior is less likely to make it into the core library. The description on the Wiki is also not very clear, so it at the very least requires some experimentation with LTSpice. I'm assuming that the PWL is kind of "started" if a certain expression resolves to true. The core library does not parse expressions, so maybe Spice#.Behavioral would be the closest thing.

[shubha-awasthi]

Thank you, Sven, for addressing the issue. I’ve found Spice#.Behavioral to be a powerful and intuitive tool.

[marcin-golebiowski]

Also you can use SpiceSharp#Behavioral

Pulse example with SpiceSharp#Behavioral
V1 a 0 PULSE(0 5 1ms 1ms 1ms 10ms 20ms)
V2 b 0 {if(TIME > 60ms, 0, 1)}
V3 c 0 {V(a) * V(b)}
.TRAN 0.001 1
.PLOT V(a)
.PLOT V(b)
.PLOT V(c)
.END

[shubha-awasthi]

@marcin-golebiowski Thank you so much. The SpiceSharp#Behavorial works great :)