It would bear noting that the model dependent on Vgd is essentially bogus. I've never seen a MOSFET like that. VDMOS is dependent on Vds for both Cgd and Cds. Seems unintuitive, but that's how it is!
Here's an implementation from one of my models,
- Diode junction capacitance model, dependent on 3rd terminal.
- Use for G, D, S as MOSFET Crss. .SUBCKT C_CJO2 1 2 4 PARAMS: CJO=10p M=0.5 VJ=0.75 E1 3 2 1 2 1.0 C1 3 2 {CJO} BI 2 1 I={I(E1) * EXP(LIMIT(LN((ABS(V(2,4)) / VJ) + 1) * M * -1, -40, 40))} .ENDS
Note that it isn't limited on M as some simulators are (why?!). Values from
3 to 20 (more than 20 gives diminishing returns) fit SJ devices pretty well.
I also haven't seen a device that shows nearly as pronounced of a kink as the datasheet suggests. Here's a real measurement:
formatting link
I have no idea how or why everyone shows a kink. It's not actually there.
Tim
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/
"Winfield Hill" wrote in message
news:q7mdl3022ad@drn.newsguy.com...
> Design of circuits using power MOSFETs is an
> important part of what we do. It's a favorite
> topic, and we talked about it plenty in AoE 3rd.
> Our upcoming x-Chapter book, that's filled with
> advanced material, has about 130 pages on the
> subject. See Dropbox for a mini-section draft
> about MOSFET SPICE models and capacitance. It
> goes after a lengthy section discussing specific
> MOSFET part aspects, and implications. You could
> make a printout to better follow the details.
>
> https://www.dropbox.com/sh/9nhm5fxm8zwsei3/AAB0lYLZmwXkOl-FeG8fuDfea?dl=0
>
> Let me know what you think.
>
>
> --
> Thanks,
> - Win