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Better power MOSFET models in LTSpice
Better power MOSFET models in LTSpice
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Old 18th August 2015, 07:14 AM   #101
keantoken is online now keantoken  United States
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I'm still pretty preoccupied, but it's been on my mind.
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Old 19th August 2015, 04:29 PM   #102
keantoken is online now keantoken  United States
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Since I wasn't able to get to this, I talked to a friend and he was up to making the model. So here is the result:

*DN2540-Tjp VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model DN2540-Tjp VDMOS (Rg=1 Vto={-1.52-4.5m*(Tjp-25)} Lambda=6m
+ Rs={0.35*(1+3m*(Tjp-25))} Kp={800m/(1+6m*(Tjp-25))}
+ Ksubthres={0.11} Mtriode={0.35} Rd={6*(1+3m*(Tjp-25))}
+ Cgdmax=10p Cgdmin=1p a=0.25 Cgs=100p Cjo=200p
+ m=0.7 VJ=2.5 IS=4.0E-8 N=2.4 Rb=10 )

You must add

.param Tjp=25

to the schematic, where 25 is the junction temperature. So if you want to go to 50C junction temperature, change Tjp to 50.

If desired, I can post models for fixed temperatures with no need of the Tjp command, although it is easy to change the model yourself if you examine how Tjp is being used.
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Old 19th August 2015, 05:23 PM   #103
bwaslo is offline bwaslo  United States
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Better power MOSFET models in LTSpice
Thanks very much, Keantoken (and Ian)!

Is there a writeup somewhere describing the process for doing this?
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Old 19th August 2015, 05:26 PM   #104
keantoken is online now keantoken  United States
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I will post a new thread with details like that (maybe soon), so that we can keep this one more beginner-friendly.
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Old 21st October 2015, 11:41 PM   #105
lhquam is offline lhquam  United States
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I am trying to tune the vdmos model parameters for measurement data of IRPF240 and IRFP9240 MOSFETs. Without the model equations the only way I have to do this is comparing simulation results to the measurement data. If I had the model equations, I could perform least-squares adjustment. Where might I find the model equations?
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Old 21st October 2015, 11:58 PM   #106
Mark Johnson is offline Mark Johnson  United States
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Better power MOSFET models in LTSpice
Quote:
Originally Posted by lhquam View Post
Where might I find the model equations [for VDMOS] ?
In the LTSPICE help file.

Help ----> Help topics ----> Contents ----> LTSPICE_IV (expand) ----> LTspice (expand) ----> Circuit elements (expand) -----> M. MOSFET

Scroll down to the paragraph that begins with "Traditionally, elaborate subcircuits have been used ...."
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Old 22nd October 2015, 12:21 AM   #107
lhquam is offline lhquam  United States
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My problem is understanding the mtriode and ksubthresh parameters and their contributions to the model equations. I have not found any documentation for those modifications to the equations.
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Old 23rd October 2015, 07:17 PM   #108
keantoken is online now keantoken  United States
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ksubthres is roughly equal to the subthreshold slope, but something like 10-20% smaller. In other words, if your FET has a subthreshold slope of 250mV/decade Id, then ksubthres would probably be somewhere from 0.2 to 0.225. No one is sure exactly which equations LTSpice uses. Your best bet is to ask Mike himself, with the email address provided in the Help menu of LTSpice.
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Old 23rd October 2015, 07:29 PM   #109
keantoken is online now keantoken  United States
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Here are new models for the IRF640/9640! The usage is the same as the previous models. For the Tjp models, the Tjp parameter must be given on the schematic ('.param Tjp=75'). The 25C and 75C models represent 25C or 75C junction temperature, and can be used like any other MOSFET model.

Thanks to Bob Cordell for the capacitance parameters.

Code:
*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF640-25C VDMOS (Rg=5 Vto={4.30-6m} Lambda=3m
+ Rs={35m*(1+3.5m)} Kp={13.0/(1+8.8m)}
+ Ksubthres={0.23*(1+4m)} Mtriode={0.35} Rd={0.1*(1+5m)}
+ Cgdmax=2600p Cgdmin=10p a=0.35 Cgs=1250p Cjo=3000p 
+ m=0.75 VJ=5 IS=1n N=1.3 Rb=0.01 )

*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF9640-25C VDMOS (pchan Rg=6 Vto={-3.76+2.5m*} Lambda=4m
+ Rs={68m*(1+3m)} Kp={9.0/(1+3m)}
+ Ksubthres={0.2*(1+4m)} Mtriode={0.3} Rd={0.25*(1+9m)}
+ Cgdmax=1200p Cgdmin=15p a=0.26 Cgs=1130p Cjo=2070p 
+ m=0.75 VJ=2.5 IS=1p N=1.5 Rb=0.02 )

*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF640-75C VDMOS (Rg=5 Vto={4.30-6m*50} Lambda=3m
+ Rs={35m*(1+3.5m*50)} Kp={13.0/(1+8.8m*50)}
+ Ksubthres={0.23*(1+4m*50)} Mtriode={0.35} Rd={0.1*(1+5m*50)}
+ Cgdmax=2600p Cgdmin=10p a=0.35 Cgs=1250p Cjo=3000p 
+ m=0.75 VJ=5 IS=1n N=1.3 Rb=0.01 )

*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF9640-75C VDMOS (pchan Rg=6 Vto={-3.76+2.5m*50} Lambda=4m
+ Rs={68m*(1+3m*50)} Kp={9.0/(1+3m*50)}
+ Ksubthres={0.2*(1+4m*50)} Mtriode={0.3} Rd={0.25*(1+9m*50)}
+ Cgdmax=1200p Cgdmin=15p a=0.26 Cgs=1130p Cjo=2070p 
+ m=0.75 VJ=2.5 IS=1p N=1.5 Rb=0.02 )

*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF640-Tjp VDMOS (Rg=5 Vto={4.30-6m*(Tjp-25)} Lambda=3m
+ Rs={35m*(1+3.5m*(Tjp-25))} Kp={13.0/(1+8.8m*(Tjp-25))}
+ Ksubthres={0.23*(1+4m*(Tjp-25))} Mtriode={0.35} Rd={0.1*(1+5m*(Tjp-25))}
+ Cgdmax=2600p Cgdmin=10p a=0.35 Cgs=1250p Cjo=3000p 
+ m=0.75 VJ=5 IS=1n N=1.3 Rb=0.01 )

*VDMOS with subthreshold (c) Ian Hegglun Aug 2015
.model IRF9640-Tjp VDMOS (pchan Rg=6 Vto={-3.76+2.5m*(Tjp-25)} Lambda=4m
+ Rs={68m*(1+3m*(Tjp-25))} Kp={9.0/(1+3m*(Tjp-25))}
+ Ksubthres={0.2*(1+4m*(Tjp-25))} Mtriode={0.3} Rd={0.25*(1+9m*(Tjp-25))}
+ Cgdmax=1200p Cgdmin=15p a=0.26 Cgs=1130p Cjo=2070p 
+ m=0.75 VJ=2.5 IS=1p N=1.5 Rb=0.02 )
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Last edited by keantoken; 23rd October 2015 at 07:37 PM.
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Old 24th October 2015, 04:42 PM   #110
lhquam is offline lhquam  United States
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Quote:
Originally Posted by keantoken View Post
ksubthres is roughly equal to the subthreshold slope, but something like 10-20% smaller. In other words, if your FET has a subthreshold slope of 250mV/decade Id, then ksubthres would probably be somewhere from 0.2 to 0.225. No one is sure exactly which equations LTSpice uses. Your best bet is to ask Mike himself, with the email address provided in the Help menu of LTSpice.

I found these lecture notes about"The MOS Transistor in Weak Inversion",
which discusses the EKV model on pages 13&14 including the subthreshold calculations: http://www.ece.utah.edu/~harrison/ec...bthreshold.pdf
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