Some LT Spice models have invisible internal nodes that are hard ground. So you can't float them off ground. LTC4444 mosfet driver for example, half-bridge with + and - power rails. Bummer. I'll just fake the gate driver with a couple of BVs. That will run faster anyhow. I guess I could run the 4444 grounded and AC couple into the gates with DC restore. Lotta hassle. -- Anybody can count to one. - Robert Widlar
internal nodes GRRRRR
Started by ●May 28, 2022
Reply by ●May 28, 20222022-05-28
jlarkin@highlandsniptechnology.com wrote:> Some LT Spice models have invisible internal nodes that are hard > ground. So you can't float them off ground. > > LTC4444 mosfet driver for example, half-bridge with + and - power > rails. Bummer.Haven't run into that one for a built-in LTspice model. Maybe it's one of the post-Engelhardt ones. Do they have a PSPICE model? If so, it could maybe be fixed with a search+replace.> > I'll just fake the gate driver with a couple of BVs. That will run > faster anyhow. > > I guess I could run the 4444 grounded and AC couple into the gates > with DC restore. Lotta hassle.Or a 1-ps transmission line--duelling bugs! 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 http://hobbs-eo.com
Reply by ●May 28, 20222022-05-28
On Sat, 28 May 2022 18:25:49 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>jlarkin@highlandsniptechnology.com wrote: >> Some LT Spice models have invisible internal nodes that are hard >> ground. So you can't float them off ground. >> >> LTC4444 mosfet driver for example, half-bridge with + and - power >> rails. Bummer. > >Haven't run into that one for a built-in LTspice model. Maybe it's one >of the post-Engelhardt ones. > >Do they have a PSPICE model? If so, it could maybe be fixed with a >search+replace. >> >> I'll just fake the gate driver with a couple of BVs. That will run >> faster anyhow. >> >> I guess I could run the 4444 grounded and AC couple into the gates >> with DC restore. Lotta hassle. > >Or a 1-ps transmission line--duelling bugs! > >Cheers > >Phil HobbsThat's a neat idea. A txline is a DC-coupled 1:1 transformer. -- Anybody can count to one. - Robert Widlar
Reply by ●May 29, 20222022-05-29
On Sat, 28 May 2022 09:32:41 -0700, jlarkin@highlandsniptechnology.com wrote:>Some LT Spice models have invisible internal nodes that are hard >ground. So you can't float them off ground. > >LTC4444 mosfet driver for example, half-bridge with + and - power >rails. Bummer. > >I'll just fake the gate driver with a couple of BVs. That will run >faster anyhow. > >I guess I could run the 4444 grounded and AC couple into the gates >with DC restore. Lotta hassle.Assuming that's really the problem: You can create a node that serves as YOUR ground. Call in GND or whatever. If there are 2xmodels with internal common nodes, I don't think you can isolate between them. I'd consult LTspice@groups.io . I generally don't use their models, unless they serve as equivalents to more generic devices or do somethging unique that justifies cost of real part use. RL
Reply by ●May 29, 20222022-05-29
On Sun, 29 May 2022 13:22:54 -0400, legg <legg@nospam.magma.ca> wrote:>On Sat, 28 May 2022 09:32:41 -0700, jlarkin@highlandsniptechnology.com >wrote: > >>Some LT Spice models have invisible internal nodes that are hard >>ground. So you can't float them off ground. >> >>LTC4444 mosfet driver for example, half-bridge with + and - power >>rails. Bummer. >> >>I'll just fake the gate driver with a couple of BVs. That will run >>faster anyhow. >> >>I guess I could run the 4444 grounded and AC couple into the gates >>with DC restore. Lotta hassle. > >Assuming that's really the problem:Maybe not. I can apply 100 volts to all pins of the LTC4444 and no current flows. There must be some other reason it won't swing to a V- rail.> >You can create a node that serves as YOUR ground. Call in GND or >whatever. If there are 2xmodels with internal common nodes, I >don't think you can isolate between them.I'm making a floating 3-phase AC power supply, with three half-bridges switching between +60 and -60. I have a floating common called N, namely the neutral of a 3-phase wye system. It's another PM alternator simulator. It's a nuisance to simulate. And very slow.> >I'd consult LTspice@groups.io . > >I generally don't use their models, unless they serve as equivalents >to more generic devices or do somethging unique that justifies >cost of real part use. > >RLSomething exotic like this mosfet driver is worth simulating with a good model. And it's worth paying more for a part with a good model, which is I guess the point of free LT Spice. -- Anybody can count to one. - Robert Widlar
Reply by ●May 29, 20222022-05-29
legg wrote:> On Sat, 28 May 2022 09:32:41 -0700, > jlarkin@highlandsniptechnology.com wrote: > >> Some LT Spice models have invisible internal nodes that are hard >> ground. So you can't float them off ground. >> >> LTC4444 mosfet driver for example, half-bridge with + and - power >> rails. Bummer. >> >> I'll just fake the gate driver with a couple of BVs. That will run >> faster anyhow. >> >> I guess I could run the 4444 grounded and AC couple into the gates >> with DC restore. Lotta hassle. > > Assuming that's really the problem: > > You can create a node that serves as YOUR ground. Call in GND or > whatever. If there are 2xmodels with internal common nodes, I don't > think you can isolate between them. > > I'd consult LTspice@groups.io . > > I generally don't use their models, unless they serve as equivalents > to more generic devices or do somethging unique that justifies cost > of real part use. >Plus their part selector is horrible--there's no way to search on parameters, or even device type. 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 http://hobbs-eo.com
Reply by ●May 29, 20222022-05-29
On Sat, 28 May 2022 16:20:48 -0700, jlarkin@highlandsniptechnology.com wrote:>On Sat, 28 May 2022 18:25:49 -0400, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>jlarkin@highlandsniptechnology.com wrote: >>> Some LT Spice models have invisible internal nodes that are hard >>> ground. So you can't float them off ground. >>> >>> LTC4444 mosfet driver for example, half-bridge with + and - power >>> rails. Bummer. >> >>Haven't run into that one for a built-in LTspice model. Maybe it's one >>of the post-Engelhardt ones. >> >>Do they have a PSPICE model? If so, it could maybe be fixed with a >>search+replace. >>> >>> I'll just fake the gate driver with a couple of BVs. That will run >>> faster anyhow. >>> >>> I guess I could run the 4444 grounded and AC couple into the gates >>> with DC restore. Lotta hassle. >> >>Or a 1-ps transmission line--duelling bugs! >> >>Cheers >> >>Phil Hobbs > >That's a neat idea. A txline is a DC-coupled 1:1 transformer.You'll have the same issues placing digital logic on flying nodes. RL
Reply by ●May 29, 20222022-05-29
legg wrote:> On Sat, 28 May 2022 16:20:48 -0700, jlarkin@highlandsniptechnology.com > wrote: > >> On Sat, 28 May 2022 18:25:49 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> jlarkin@highlandsniptechnology.com wrote: >>>> Some LT Spice models have invisible internal nodes that are hard >>>> ground. So you can't float them off ground. >>>> >>>> LTC4444 mosfet driver for example, half-bridge with + and - power >>>> rails. Bummer. >>> >>> Haven't run into that one for a built-in LTspice model. Maybe it's one >>> of the post-Engelhardt ones. >>> >>> Do they have a PSPICE model? If so, it could maybe be fixed with a >>> search+replace. >>>> >>>> I'll just fake the gate driver with a couple of BVs. That will run >>>> faster anyhow. >>>> >>>> I guess I could run the 4444 grounded and AC couple into the gates >>>> with DC restore. Lotta hassle. >>> >>> Or a 1-ps transmission line--duelling bugs! >>> >>> Cheers >>> >>> Phil Hobbs >> >> That's a neat idea. A txline is a DC-coupled 1:1 transformer. > > You'll have the same issues placing digital logic on flying > nodes. > > RL >More tlines! Cheers Phil "Everything's a transmission line anyway" 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 http://hobbs-eo.com
Reply by ●May 29, 20222022-05-29
On Sun, 29 May 2022 16:22:53 -0400, legg <legg@nospam.magma.ca> wrote:>On Sat, 28 May 2022 16:20:48 -0700, jlarkin@highlandsniptechnology.com >wrote: > >>On Sat, 28 May 2022 18:25:49 -0400, Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>>jlarkin@highlandsniptechnology.com wrote: >>>> Some LT Spice models have invisible internal nodes that are hard >>>> ground. So you can't float them off ground. >>>> >>>> LTC4444 mosfet driver for example, half-bridge with + and - power >>>> rails. Bummer. >>> >>>Haven't run into that one for a built-in LTspice model. Maybe it's one >>>of the post-Engelhardt ones. >>> >>>Do they have a PSPICE model? If so, it could maybe be fixed with a >>>search+replace. >>>> >>>> I'll just fake the gate driver with a couple of BVs. That will run >>>> faster anyhow. >>>> >>>> I guess I could run the 4444 grounded and AC couple into the gates >>>> with DC restore. Lotta hassle. >>> >>>Or a 1-ps transmission line--duelling bugs! >>> >>>Cheers >>> >>>Phil Hobbs >> >>That's a neat idea. A txline is a DC-coupled 1:1 transformer. > >You'll have the same issues placing digital logic on flying >nodes. > >RLYes. They are ground referenced for sure. -- John Larkin Highland Technology, Inc trk The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"
