Guys, I know most of you are experienced users of spice here :) Two short questions, I've already RTM without find the answers. - I need a TIP 122 model... where I should look for? - worst-case scenario: I set the tolerances of my resistors. How to run a simulation to get the worst-case? I'm talking about the maximum span of selected traces when components reach their end values. Thanks! Marco
Two questions about LTSpice
Started by ●October 17, 2012
Reply by ●October 17, 20122012-10-17
Hello For the TIP122, I did a search on Google and I got it within the first hit. As for the worst-case setup, try this link, it has a good explanation: k6jca.blogspot.com/2012/07/monte-carlo-and-worst-case-circuit.html Good luck, Vlad
Reply by ●October 17, 20122012-10-17
Il 17/10/2012 08:46, Vlad ha scritto:> For the TIP122, I did a search on Google and I got it within the first hit.I also got it at the first hit, if you're referring to this page: http://www.onsemi.com/pub_link/Collateral/TIP122.SP2 but the code inside is quite different than the *.asy files available into the lib folder of LTSpice. Here my question. In fact I've already tried to put the file there calling it tip122.asy. But when I select it from LTSpice I got 'Unknown symbol syntax: ".SUBCKT Xtip122 1 2 3" '> As for the worst-case setup, try this link, it has a good explanation: k6jca.blogspot.com/2012/07/monte-carlo-and-worst-case-circuit.htmlThanks a lot for the link. I'll give it a try. Marco
Reply by ●October 17, 20122012-10-17
On 10/17/2012 09:13 AM, Marco Trapanese wrote:> Il 17/10/2012 08:46, Vlad ha scritto: > >> For the TIP122, I did a search on Google and I got it within the first >> hit. > > > I also got it at the first hit, if you're referring to this page: > > http://www.onsemi.com/pub_link/Collateral/TIP122.SP2 > > but the code inside is quite different than the *.asy files available > into the lib folder of LTSpice. Here my question. > > In fact I've already tried to put the file there calling it tip122.asy. > But when I select it from LTSpice I got 'Unknown symbol syntax: ".SUBCKT > Xtip122 1 2 3" ' > > >> As for the worst-case setup, try this link, it has a good explanation: >> k6jca.blogspot.com/2012/07/monte-carlo-and-worst-case-circuit.html > > > Thanks a lot for the link. I'll give it a try. > > Marco > >The link Vlad provided is a Spice subcircuit file. Perhaps this http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_4.htm may help you inserting it into LTSpice. Pere
Reply by ●October 17, 20122012-10-17
Il 17/10/2012 09:55, o pere o ha scritto:> The link Vlad provided is a Spice subcircuit file. Perhaps this > http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_4.htm > may help you inserting it into LTSpice.Thanks! I wasn't able to find this information in the manual. It works. Marco
Reply by ●October 17, 20122012-10-17
On Oct 16, 9:44=A0pm, Marco Trapanese <marcotrapaneseNOS...@gmail.com> wrote:> Guys, I know most of you are experienced users of spice here :) > Two short questions, I've already RTM without find the answers. > > - I need a TIP 122 model... where I should look for? > > - worst-case scenario: I set the tolerances of my resistors. How to run > a simulation to get the worst-case? I'm talking about the maximum span > of selected traces when components reach their end values. > > Thanks! > MarcoAre you certain you want ALL the worst case values at the SAME time? The statistical likelihood of that is supposed to be extremely small. We only used the 'worst case box' for milspec designs, where if the circuit didn't perform to spec, you had to point tothe component that was out of spec, else... More likely scenario was for cmmecial designs where we used a Guassian distribution for the component tolerances, like 'square root of the sum of the squares' tolerances which was quite a bit more lenient to design. But even in Production that wasn't realistic - sometimes. We found the resistor manufacturers made runs of resistors measured what thy made, which created a flat distribution, but then they culled out special values which put 'holes' in that distribution! Usually we got distributions with the centers cut out. In other words likely to get + values and like to get - values, and rarely got exactly what the label said.
Reply by ●October 17, 20122012-10-17
Il 17/10/2012 16:04, Robert Macy ha scritto:> Are you certain you want ALL the worst case values at the SAME time? > The statistical likelihood of that is supposed to be extremely small.Small is not zero, and Murphy's watching me :)> More likely scenario was for cmmecial designs where we used a Guassian > distribution for the component tolerances, like 'square root of the > sum of the squares' tolerances which was quite a bit more lenient to > design. But even in Production that wasn't realistic - sometimes. We > found the resistor manufacturers made runs of resistors measured what > thy made, which created a flat distribution, but then they culled out > special values which put 'holes' in that distribution! Usually we got > distributions with the centers cut out. In other words likely to get + > values and like to get - values, and rarely got exactly what the label > said.I'm agree, but sometimes is useful to know where are the bounding limits, hoping you'll never reach them. Marco
Reply by ●October 17, 20122012-10-17
Il 17/10/2012 08:46, Vlad ha scritto:> As for the worst-case setup, try this link, it has a good explanation:> k6jca.blogspot.com/2012/07/monte-carlo-and-worst-case-circuit.html It does the dirty job but in a weird way. I'm going to improve it. Do you know a way to obtain the tolerance value already put in the related field (e.g. a resistor) ? Marco
Reply by ●October 17, 20122012-10-17
On 10/16/2012 11:44 PM, Marco Trapanese wrote:> Guys, I know most of you are experienced users of spice here :) > Two short questions, I've already RTM without find the answers. > > - I need a TIP 122 model... where I should look for? > > - worst-case scenario: I set the tolerances of my resistors. How to run > a simulation to get the worst-case? I'm talking about the maximum span > of selected traces when components reach their end values. > > Thanks! > MarcoThere is an example simulation that comes with LTSpice called MonteCarlo.asc in the \LTC\LTspiceIV\examples\Educational folder. You don't have to do the Monte Carlo, but the example is good to study to see how to change component values as you wish. Cheers, JohnS
Reply by ●October 17, 20122012-10-17
On Wed, 17 Oct 2012 09:55:34 +0200, o pere o <me@somewhere.net> wrote:>On 10/17/2012 09:13 AM, Marco Trapanese wrote: >> Il 17/10/2012 08:46, Vlad ha scritto: >> >>> For the TIP122, I did a search on Google and I got it within the first >>> hit. >> >> >> I also got it at the first hit, if you're referring to this page: >> >> http://www.onsemi.com/pub_link/Collateral/TIP122.SP2 >> >> but the code inside is quite different than the *.asy files available >> into the lib folder of LTSpice. Here my question. >> >> In fact I've already tried to put the file there calling it tip122.asy. >> But when I select it from LTSpice I got 'Unknown symbol syntax: ".SUBCKT >> Xtip122 1 2 3" ' >> >> >>> As for the worst-case setup, try this link, it has a good explanation: >>> k6jca.blogspot.com/2012/07/monte-carlo-and-worst-case-circuit.html >> >> >> Thanks a lot for the link. I'll give it a try. >> >> Marco >> >> > >The link Vlad provided is a Spice subcircuit file. Perhaps this >http://www.simonbramble.co.uk/lt_spice/ltspice_lt_spice_tutorial_4.htm >may help you inserting it into LTSpice. > >PereSince I work primarily at the device level I literally have hundreds of libraries. Is there a way in LTspice to call a library by its PATH, rather than requiring it to be in the same folder as the schematic? ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
