LTSPICE: startup

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Chris Carlen 21 years ago

Greetings:

Wouldn't it be nice if SPICE allowed one to set the output voltage/current of independent sources for computing the operating point individually per source?

I realize LTSPICE has the "startup" option which can be a help, but sometimes I want only one source turned off while the others, like power supplies are left on. I find myself building klunky constructs such as a pulse source called "delay" which actuates switches to release desired sources after a specified time.

Also, the startup option in LTSPICE is limited to operating after 5us. Why the fixed time?

Is it possible to have a new option for indep. sources called "Vdelay" which sets the output voltage (speaking specifically here about V sources, of course) during the "Tdelay" period instead of having that output be set by "Vinitial"?

That would solve this problem in the most fine grained manner perhaps?

Thanks for comments.

Good day!

_____________________ Christopher R. Carlen crobc@bogus-remove-me.sbcglobal.net SuSE 9.1 Linux 2.6.5

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Jim Thompson 21 years ago

Sno-o-o-ort ;-)

In PSpice...

STP(x) 1 if x>0.0, 0 if x

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Jim Thompson 21 years ago

I'm not surprised either.

...Jim Thompson

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Joerg 21 years ago

Hello Chris,

So that Jim can't use LTSpice for his fast IC stuff ....?

Regards, Joerg

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Helmut Sennewald 21 years ago

----- Original Message ----- From: "Jim Thompson" Newsgroups: sci.electronics.cad Sent: Tuesday, May 17, 2005 11:46 PM Subject: Re: LTSPICE: startup

Hello Jim,

LTspice has a function u(x) which has the same definition as your STP(x). It can be used with B(ehavioral)-sources as well as with E-sources. Your example would then look like

V=V(1)*u(TIME-10ns)

or

with Epoly:

VALUE={V(1)*u(TIME-10ns)}

But as usual I am not surprised that LTspice also understands

V=V(1)*STP(TIME-10ns)

or with Epoly:

VALUE={V(1)*STP(TIME-10ns)}

Best regards, Helmut

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Robert Baer 21 years ago

Undefined for x=0?

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Jim Thompson 21 years ago

Pasted directly from the Reference Guide, but should be x >= 0

...Jim Thompson

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Chris Carlen 21 years ago

That should suffice to meet my wishes. Thanks.

_______________________________________________________________________ Christopher R. Carlen Principal Laser/Optical Technologist Sandia National Laboratories CA USA crcarleRemoveThis@BOGUSsandia.gov NOTE, delete texts: "RemoveThis" and "BOGUS" from email address to reply.

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LTSPICE: startup

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