LTSPICE: startup

C

Chris Carlen

Guest
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
 
Hello Chris,

Also, the startup option in LTSPICE is limited to operating after 5us.
Why the fixed time?
Click to expand...
So that Jim can't use LTSpice for his fast IC stuff ....?

Regards, Joerg

http://www.analogconsultants.com
 
On Tue, 17 May 2005 21:33:31 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Chris,

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

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

Regards, Joerg

http://www.analogconsultants.com
Click to expand...
Sno-o-o-ort ;-)

In PSpice...

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

The unit step function can be used to suppress a value until a given
amount of time has passed.

For instance,

{v(1)*STP(TIME-10ns)}

gives a value of 0.0 until 10ns has elapsed, then gives v(1).

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
----- Original Message -----
From: "Jim Thompson" <thegreatone@example.com>
Newsgroups: sci.electronics.cad
Sent: Tuesday, May 17, 2005 11:46 PM
Subject: Re: LTSPICE: startup


On Tue, 17 May 2005 21:33:31 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello Chris,

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

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

Regards, Joerg

http://www.analogconsultants.com

Sno-o-o-ort ;-)

In PSpice...

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

The unit step function can be used to suppress a value until a given
amount of time has passed.

For instance,

{v(1)*STP(TIME-10ns)}

gives a value of 0.0 until 10ns has elapsed, then gives v(1).

...Jim Thompson
Click to expand...
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
 
On Wed, 18 May 2005 00:05:21 +0200, "Helmut Sennewald"
<helmutsennewald@t-online.de> wrote:

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


On Tue, 17 May 2005 21:33:31 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:

Hello Chris,

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

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

Regards, Joerg

http://www.analogconsultants.com

Sno-o-o-ort ;-)

In PSpice...

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

The unit step function can be used to suppress a value until a given
amount of time has passed.

For instance,

{v(1)*STP(TIME-10ns)}

gives a value of 0.0 until 10ns has elapsed, then gives v(1).

...Jim Thompson

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
Click to expand...
I'm not surprised either.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote:

On Tue, 17 May 2005 21:33:31 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


Hello Chris,


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

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

Regards, Joerg

http://www.analogconsultants.com


Sno-o-o-ort ;-)

In PSpice...

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

The unit step function can be used to suppress a value until a given
amount of time has passed.

For instance,

{v(1)*STP(TIME-10ns)}

gives a value of 0.0 until 10ns has elapsed, then gives v(1).

...Jim Thompson
Undefined for x=0?
Click to expand...
 
On Wed, 18 May 2005 06:18:43 GMT, Robert Baer
<robertbaer@earthlink.net> wrote:

Jim Thompson wrote:

On Tue, 17 May 2005 21:33:31 GMT, Joerg
notthisjoergsch@removethispacbell.net> wrote:


Hello Chris,


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

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

Regards, Joerg

http://www.analogconsultants.com


Sno-o-o-ort ;-)

In PSpice...

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

The unit step function can be used to suppress a value until a given
amount of time has passed.

For instance,

{v(1)*STP(TIME-10ns)}

gives a value of 0.0 until 10ns has elapsed, then gives v(1).

...Jim Thompson
Undefined for x=0?
Click to expand...
Pasted directly from the Reference Guide, but should be x >= 0

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Helmut Sennewald wrote:
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
Click to expand...


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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