# HSPICE question

Discussion in 'General Electronics' started by Sanjayan Vinayagamoorthy, Dec 14, 2003.

1. ### Sanjayan VinayagamoorthyGuest

Hello,

I have a couple of questions regarding hspice and I hope that someone
would be able to help me out of point me in the right direction.

When using the measure statement in hspice is there a method of
determining at what time a certain event occured. For example,
..MEASURE TRAN DesiredVal FIND I(Vmeas) WHEN v(1) = 1V.
This will make DesiredVal be equal to the current throught Vmeas when
v(1) is 1V. Is it possible to find the time when v(1) is 1V.

My next question is how does one do a switch in hspice. I assume that
it would have to be a voltage controlled resistor but I am not sure
how to do it.

If someone can help me with the above queries I would really
appreciate it.

Thanks,

Sanjay

2. ### MikeGuest

1. Yes. Leave off the FIND option. Here's an example:

* HSPICE Test File
vin vo 0 pwl 0.0n 0.0v 100n 1.0v
rox vo vx 1k
rxo vx 0 1k
* Measure vx when vo = 0.5
..measure tran vx1 FIND v(vx) WHEN v(vo)=0.5 TD = 0.0n
* Measure time when v(vo) = 0.5
..measure tran tx1 WHEN v(vo)=0.5 TD = 0.0n
..probe tran v(vo) v(vx)
..tran 1n 100n
..end

The measure output is:

****** transient analysis tnom= 25.000 temp= 25.000

tx1= 5.0000E-08
vx1= 2.5000E-01

2. There is an element called, appropriately enough, a "Voltage Controlled
Resistor." It's an extension of the Voltage Controlled Current Source model
(G).

Gres n1 n2 VCR c1 c2 <more parameters required>

This is all in the HSPICE documentation.

I accept appreciation through PayPal, or you can just gush uncontrollably
in a followup post. ;-)

-- Mike --

3. ### Sanjayan VinayagamoorthyGuest

Hello,

In following the grand old tradition of being a poor student, I will
choose the latter. Your help has been greatly appreciated. It has a
been a lighthouse, shining brightly through the thick fog of
uncertainty. Where I once walked in trepidation, I can now step boldly
into the "spice" storms that await me. I would go on, but my
vernacular has drastically decreased through university.

Kidding aside, I appreciate your time.

Regards,
Sanjay

4. ### MikeGuest

Oh, stop, you're making me blush. ;-) Sorry about your vernacular - think
of it as one of many sacrifices you'll have to make for an education. Just
wait till you see the humiliating gown they'll make you wear for

One of my more useful binders is a collection of HSPICE notes. Years ago,
the HSPICE documentation didn't even include an index, so my notes were
useful as much for their organization as anything else. Even today, I still
have my notes, since the current documentation provides a cryptic comment
that says FIND WHEN can be used to return the time, but gives no examples
and makes no mention that the FIND portion of FIND WHEN must be left off.
They even go so far as to state, in a different chapter, that "time" is a
reserved keyword, making you think that you can use it as the argument to
FIND. Alas, that is not the case.

I also have a rather large template file (I have one for HSPICE and another
for Eldo) that contains various example snippets like the ones above, along
with copious notes to myself.

-- Mike --

5. ### Sanjayan VinayagamoorthyGuest

Oh, stop, you're making me blush. ;-) Sorry about your vernacular - think
Hello,

That's cool. I am sort of new to circuits myself, which is why I have
tonnes of questions regarding hspice. I am appreciative of the fact
that you oblige me by answering them. Do you by any chance have
reservations against sending some of those nice snippets of "hspice"
code along? I completely understand if they are a private collection,
but I couldn't help asking .

Thanks again,

Regards,
Sanjay