Modeling Notes

VDMOS

The vdmos-static-fast emitter maps datasheet values into a compact power MOSFET model starter.

Typical mapping:

• Vto: threshold voltage.
• Kp: transconductance starter from gfs and RDS(on).
• Rd/Rs: split from RDS(on).
• Rg: internal gate resistance.
• Cgs: high-voltage Ciss - Crss.
• Cgdmin: high-voltage Crss.
• Cgdmax: low-voltage Crss.
• Cjo: high-voltage Coss - Crss.
• Tt: reverse recovery starter from Qrr/IF or trr.

For ltspice and ngspice, this is emitted as a native .model ... VDMOS(...) card. For common, pspice, hspice, xyce, and experimental qspice, the emitter writes a portable MOS fallback subcircuit with fixed capacitances and a simple NMOS LEVEL=1 channel. The fallback is useful for topology and deck checks, but it is not equivalent to a native VDMOS implementation.

This family is fast, but not enough for high-fidelity switching waveforms without fitting.

ABM Basic

The abm-basic emitter uses:

• smooth Idsat(Vgs) plus RDS(on) channel current,
• nonlinear Cgs/Cgd/Cds from datasheet capacitance curves,
• simple body diode,
• explicit package/gate parasitics.

The current capacitance implementation is a starter. For better convergence and accuracy, future work should replace table capacitances with smoothed charge functions.

See SPICE Dialects for the supported netlist dialects and the boundary between native VDMOS and portable fallback exports.

Diode Basic

The diode-basic emitter writes a portable two-terminal subcircuit around a native SPICE D model card. It maps datasheet values into starter parameters:

• BV from VRRM or reverse-voltage rating.
• Rs, Is, and N from a forward-voltage point and reference current.
• Cjo from junction or total capacitance.
• Tt from Qrr/IF or trr.
• Ibv from reverse leakage current when available.
• anode and cathode lead inductance/resistance from package parasitics or conservative defaults.

The generated diode model is intentionally compact and portable. It is suitable for early topology checks and first transient comparisons, then should be fitted against datasheet VF(IF), Cj(VR), thermal, and recovery curves.

Diode ABM Dynamic

The diode-abm-dynamic emitter keeps the portable two-terminal package shell but adds behavioral transient terms:

• a smoothed nonlinear Cj(VR) current source using CJO, VJ, M, and CJ_SCALE,
• a hidden qrr_state capacitor that stores forward-conduction recovery charge,
• a smoothed reverse-bias gate that releases the stored charge as recovery current using TAU and RR_SCALE,
• the same DC diode card, leakage path, and package parasitics used by the compact diode starter.

The starter fit maps CJO_pF, TRR_ns, QRR_nC, and IRRM_A into initial TAU_ns, RR_SCALE, and CJ_SCALE values. This can produce more realistic reverse-recovery transients than a plain diode TT card, but it is still a reviewable approximation. Tune it against datasheet recovery test conditions or measured waveforms before relying on switching-loss predictions.

Model Level Naming

This project avoids L1/L2/L3 names because they conflict with:

• SPICE LEVEL= model equations,
• vendor-specific model-level definitions.

Instead use:

• model_class: vdmos, abm, verilog_a
• fidelity: static, dynamic, electrothermal, lab_fitted