spice diode model question
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From: Martin Riddle on 20 Dec 2009 14:30 I have a diode that I want to model, it's a 85HF20. <http://www.vishay.com/docs/93529/85hf.pdf> This is one of those standard stud mounted rectifiers. This is the model that I created for it: ..model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) Cjo was taken for a similar sized schottky . I don't have experience with these larger diodes so the model is almost default values. I don't need the Temperature parameters. Most of the reference books , I have, don't deal with the larger diodes. Is the Is parameter correct for this model? Any pointers? I basically need to know if this slow diode will clamp a forward voltage from a inductor. the model above does work. But its no good if its wrong. ( I had another model that didn't work well) Thanks
From: Jim Thompson on 20 Dec 2009 15:46 On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" <martin_rid(a)verizon.net> wrote: >I have a diode that I want to model, it's a 85HF20. ><http://www.vishay.com/docs/93529/85hf.pdf> >This is one of those standard stud mounted rectifiers. > >This is the model that I created for it: >.model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 >Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) > >Cjo was taken for a similar sized schottky . I don't have experience >with these larger diodes so the model is almost default values. I don't >need the Temperature parameters. Most of the reference books , I have, >don't deal with the larger diodes. >Is the Is parameter correct for this model? Any pointers? > >I basically need to know if this slow diode will clamp a forward voltage >from a inductor. the model above does work. But its no good if its >wrong. ( I had another model that didn't work well) > >Thanks > The basic Spice diode equation stumbles with Schottky's. To fit DC, fiddle with IS, RS, IK, N (not M, that's for capacitance) _and_ EG. Hint: EG ~= 0.58 seems to be what most of my models use. The resulting model is NOT good over temperature. I've had fairly good results paralleling diode models with different IS's, etc., but it's a tedious curve-fitting process. ...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 | Help save the environment! Please dispose of socialism properly!
From: Jim Thompson on 20 Dec 2009 16:04 On Sun, 20 Dec 2009 13:46:58 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com/Snicker> wrote: >On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" ><martin_rid(a)verizon.net> wrote: > >>I have a diode that I want to model, it's a 85HF20. >><http://www.vishay.com/docs/93529/85hf.pdf> >>This is one of those standard stud mounted rectifiers. >> >>This is the model that I created for it: >>.model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 >>Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) >> >>Cjo was taken for a similar sized schottky . I don't have experience >>with these larger diodes so the model is almost default values. I don't >>need the Temperature parameters. Most of the reference books , I have, >>don't deal with the larger diodes. >>Is the Is parameter correct for this model? Any pointers? >> >>I basically need to know if this slow diode will clamp a forward voltage >>from a inductor. the model above does work. But its no good if its >>wrong. ( I had another model that didn't work well) >> >>Thanks >> > >The basic Spice diode equation stumbles with Schottky's. > >To fit DC, fiddle with IS, RS, IK, N (not M, that's for capacitance) >_and_ EG. > >Hint: EG ~= 0.58 seems to be what most of my models use. > >The resulting model is NOT good over temperature. I've had fairly >good results paralleling diode models with different IS's, etc., but >it's a tedious curve-fitting process. > > ...Jim Thompson Also found this page... http://www.diodes.com/products/spicemodels/index.php ...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 | Help save the environment! Please dispose of socialism properly!
From: John Larkin on 20 Dec 2009 16:03 On Sun, 20 Dec 2009 14:30:13 -0500, "Martin Riddle" <martin_rid(a)verizon.net> wrote: >I have a diode that I want to model, it's a 85HF20. ><http://www.vishay.com/docs/93529/85hf.pdf> >This is one of those standard stud mounted rectifiers. > >This is the model that I created for it: >.model 85HF20 D(BV=200 Ibv=.009 Is=1e-3 Cjo=2300p M=0.43 Rs=.00169 >Tt=100u Eg=1.11 Vj=1.2 Fc=0.5 N=1.1 ) > >Cjo was taken for a similar sized schottky . I don't have experience >with these larger diodes so the model is almost default values. I don't >need the Temperature parameters. Most of the reference books , I have, >don't deal with the larger diodes. >Is the Is parameter correct for this model? Any pointers? > >I basically need to know if this slow diode will clamp a forward voltage >from a inductor. the model above does work. But its no good if its >wrong. ( I had another model that didn't work well) > >Thanks > If you're concerned about the "forward recovery time" thing, I doubt that a model will be very useful. You'd really need to test an actual part to see how it behaves. To complicate life, several of the different voltage rated versions may at various times come off the same wafer. In general, higher voltage parts have wider junctions, approaching pin diodes for, say, 600 volt parts, and they tend to be slower turning on. I've slammed 48 volts across a 600 volt "fast recovery" diode and it took a couple hundred nanoseconds to ramp up to 50 amps. What's your circuit? John
From: Jim Thompson on 20 Dec 2009 16:25
On Sun, 20 Dec 2009 13:03:32 -0800, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >I've slammed 48 volts across a 600 volt "fast recovery" diode and >it took a couple hundred nanoseconds to ramp up to 50 amps. > [snip] > >John > Which sounds like 200nH in the wiring ;-) ...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 | Help save the environment! Please dispose of socialism properly! |