Forums

LTSpice LED parameters

Started by John S February 14, 2018
Here is what I have:

.model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA 
Vpk=5 mfg=Lumileds type=LED)

How do I change the Vf at a specified current? I suspect that it is more 
involved than just changing Rs.

Thanks, Guys.
On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org>
wrote:

>Here is what I have: > >.model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >Vpk=5 mfg=Lumileds type=LED) > >How do I change the Vf at a specified current? I suspect that it is more >involved than just changing Rs. > >Thanks, Guys.
Is changes the ideal-diode (exponential) part of the curve, and Rs changes the linear, ohmic part. LEDs get more linear, ohmic, at high currents. Just fiddle until the simulated E:I curve matches your real part. You'll get a feel for that pretty fast. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org>
wrote:

>Here is what I have: > >.model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >Vpk=5 mfg=Lumileds type=LED) > >How do I change the Vf at a specified current? I suspect that it is more >involved than just changing Rs. > >Thanks, Guys.
Iave, Vpk and "type" are NOT true Spice parameters... they are toyLTspice fudges that use LTspice-specific models that are NOT usable anywhere else. Toss those parameters completely, Set Solver=Alternate Tweak IS, Rs, N and EG to curve fit to your data. For serious work, invest in a real simulator ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | It's what you learn, after you know it all, that counts.
In message <ut998dta4trqd8umgek5oukocqro6b07gs@4ax.com>, John Larkin 
<jjlarkin@highland_snip_technology.com> writes
>On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> >wrote: > >>Here is what I have: >> >>.model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >>Vpk=5 mfg=Lumileds type=LED) >> >>How do I change the Vf at a specified current? I suspect that it is more >>involved than just changing Rs. >> >>Thanks, Guys. > >Is changes the ideal-diode (exponential) part of the curve, and Rs >changes the linear, ohmic part. LEDs get more linear, ohmic, at high >currents. > >Just fiddle until the simulated E:I curve matches your real part. >You'll get a feel for that pretty fast. > >
N affects the slope of the exponential. M and VJ the capacitance. He might want EG as well. Https://electronics.stackexchange.com/questions/9510/how-do-i-model-an-le d-with-spice B -- Brian Howie
On 02/14/2018 04:24 PM, Jim Thompson wrote:
> On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> > wrote: > >> Here is what I have: >> >> .model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >> Vpk=5 mfg=Lumileds type=LED) >> >> How do I change the Vf at a specified current? I suspect that it is more >> involved than just changing Rs. >> >> Thanks, Guys. > > Iave, Vpk and "type" are NOT true Spice parameters... they are > toyLTspice fudges that use LTspice-specific models that are NOT usable > anywhere else.
Like pspice encryption?
> > Toss those parameters completely, > > Set Solver=Alternate > > Tweak IS, Rs, N and EG to curve fit to your data. > > For serious work, invest in a real simulator ;-)
Board level models are so buggy in general that a bigger flyswatter just makes a bigger mess. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
On Wed, 14 Feb 2018 14:24:16 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> >wrote: > >>Here is what I have: >> >>.model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >>Vpk=5 mfg=Lumileds type=LED) >> >>How do I change the Vf at a specified current? I suspect that it is more >>involved than just changing Rs. >> >>Thanks, Guys. > >Iave, Vpk and "type" are NOT true Spice parameters... they are >toyLTspice fudges that use LTspice-specific models that are NOT usable >anywhere else. >
Those are basically comments; they don't affect the sims. Comments are nice. Don't you want to know part numbers? LT Spice is wonderful, and free, and is getting a lot of kids interested in electronics. Why are you so hostile? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thu, 15 Feb 2018 10:50:10 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 02/14/2018 04:24 PM, Jim Thompson wrote: >> On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> >> wrote: >> >>> Here is what I have: >>> >>> .model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >>> Vpk=5 mfg=Lumileds type=LED) >>> >>> How do I change the Vf at a specified current? I suspect that it is more >>> involved than just changing Rs. >>> >>> Thanks, Guys. >> >> Iave, Vpk and "type" are NOT true Spice parameters... they are >> toyLTspice fudges that use LTspice-specific models that are NOT usable >> anywhere else. > >Like pspice encryption?
It's not the same thing. LTspice has encryption too, you twit. .MODEL D D(...) is a standard device model format that will "play" on any other Spice-compliant simulator. Mikey's version will not. The proper way to handle such a model is to define it as a subcircuit with parameter-passing. Most LTspice models of their standard products won't "play" on any other simulator. Is that good business? TI seems to have (somewhat) caught on to the fact that they need to offer across-platform/simulator models. Wonder when Analog Devices (nee Linear) will catch on, toss Mikey, and make available compliant models? I doubt that it's long coming. The LTspice List is now consumed by questions about what LTspice doesn't do right, hangs or crashes.
> >> >> Toss those parameters completely, >> >> Set Solver=Alternate >> >> Tweak IS, Rs, N and EG to curve fit to your data. >> >> For serious work, invest in a real simulator ;-) > >Board level models are so buggy in general that a bigger flyswatter just >makes a bigger mess.
Baloney makes your head swell bigger ;-)
> >Cheers > >Phil Hobbs
...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | It's what you learn, after you know it all, that counts.
On Thu, 15 Feb 2018 09:40:28 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Thu, 15 Feb 2018 10:50:10 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>On 02/14/2018 04:24 PM, Jim Thompson wrote: >>> On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> >>> wrote: >>> >>>> Here is what I have: >>>> >>>> .model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >>>> Vpk=5 mfg=Lumileds type=LED) >>>> >>>> How do I change the Vf at a specified current? I suspect that it is more >>>> involved than just changing Rs. >>>> >>>> Thanks, Guys. >>> >>> Iave, Vpk and "type" are NOT true Spice parameters... they are >>> toyLTspice fudges that use LTspice-specific models that are NOT usable >>> anywhere else. >> >>Like pspice encryption? > >It's not the same thing. LTspice has encryption too, you twit. > >.MODEL D D(...) is a standard device model format that will "play" on >any other Spice-compliant simulator. Mikey's version will not. > >The proper way to handle such a model is to define it as a subcircuit >with parameter-passing. > >Most LTspice models of their standard products won't "play" on any >other simulator. Is that good business?
LT Spice is free! It doesn't need to be "good business" in the paid-for simulator market. What it does is sell LTC chips.
> >TI seems to have (somewhat) caught on to the fact that they need to >offer across-platform/simulator models. > >Wonder when Analog Devices (nee Linear) will catch on, toss Mikey, and >make available compliant models?
I was told that ADI will be migrating to LT Spice. I think that LT Spice is one reason they bought LTC.
> >I doubt that it's long coming. The LTspice List is now consumed by >questions about what LTspice doesn't do right, hangs or crashes.
It works perfectly for me, no hangs or crashes. I did manage to crash it once some years back, by typing a very mal-formed illegal math expression. Mike fixed that in one day.
> >> >>> >>> Toss those parameters completely, >>> >>> Set Solver=Alternate >>> >>> Tweak IS, Rs, N and EG to curve fit to your data. >>> >>> For serious work, invest in a real simulator ;-) >> >>Board level models are so buggy in general that a bigger flyswatter just >>makes a bigger mess. > >Baloney makes your head swell bigger ;-)
My, you are in a nasty mood lately. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Jim Thompson wrote:

> LTspice has encryption too, you twit.
Real mature... NOT. And I get shit on here every time I turn around. It's like the whole world ignoring how much of an ill character, honorless bastard Donald J. Trump is. Un fucking believeable.
On 02/15/2018 11:25 AM, John Larkin wrote:
> On Wed, 14 Feb 2018 14:24:16 -0700, Jim Thompson > <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >> On Wed, 14 Feb 2018 15:07:42 -0600, John S <Sophi.2@invalid.org> >> wrote: >> >>> Here is what I have: >>> >>> .model LXHL-BW02 D(Is=4.5e-20 Rs=.85 N=2.6 Cjo=1.18n Xti=200 Iave=400mA >>> Vpk=5 mfg=Lumileds type=LED) >>> >>> How do I change the Vf at a specified current? I suspect that it is more >>> involved than just changing Rs. >>> >>> Thanks, Guys. >> >> Iave, Vpk and "type" are NOT true Spice parameters... they are >> toyLTspice fudges that use LTspice-specific models that are NOT usable >> anywhere else. >> > > Those are basically comments; they don't affect the sims. > > Comments are nice. Don't you want to know part numbers? > > LT Spice is wonderful, and free, and is getting a lot of kids > interested in electronics. Why are you so hostile? > >
He's still making payments on his Pspice license. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com