Analog Power Inc. SPICE MODELING Revised August 2015 Analog Power Spice Model Goals • To provide simple, fast, accurate SPICE model to be used predominantly for switching speed and loss calculations • To be able to support model and its use • To allow temperature modeling, but not at the expense of speed and simplicity • To focus on the useful modeling parameters, and do not include breakdown voltage etc as stresses can be checked via model probing • To support on low cost universal platforms, WinSpice, NGSPICE, LT Spice • To be able to use SPICE to select the optimum part for PWM applications Not Intended for (significant added complexity/run time): • Modeling of breakdown voltage, high temperature leakage • Thermal modeling including RDS variation with temperature – Model can be adjusted for temperature • Qrr modeling Analog Power Confidential Analog Power SPICE Subcircuit Analog Power model R1.0: • Simple Level 1 model with 8 external components • Excellent fitting to data sheet curves • All parameters are devicederived not process derived • Very simple to see effects of each parameter Analog Power Confidential Analog Power SPICE Subcircuit 2.0 Improved implementation: Non-Linear dependent voltage sources used to set dv/dt over diode and fixed capacitor = zero appropriately , and therefore isolate them when not in circuit. No switches used, but identical concept Analog Power Confidential Analog Power Spice Example (switch, L1) .SUBCKT AM90N08-04B 1 2 3 *Nom Temp=25 deg C Mos1 4 5 6 6 APLMOS w=1 l=1 .MODEL APLMOS NMOS (Level=1 VTO=1.94 KP=116 CGDO = 600p CGSO = 9100p) Rdrain 1 4 4.7e-3 Dbody 6 1 BodyDiode .MODEL BodyDiode D (RS=2e-3 IS=2e-12 vj=0.6 RS=2m CJO=1000p M=0.67) Lsource 3 6 3e-9 Rgate 2 5 1.8 Dcgd 5 7 Crss .MODEL Crss D (RS=1e-3 CJO=10.9n M=1.18) Sdiode 7 1 1 5 Sfb1 Scap 8 1 5 1 Sfb2 .MODEL Sfb1 VSWITCH (RON=100m ROFF=10e11 VON=0 VOFF=-0.01) .MODEL Sfb2 VSWITCH (RON=100m ROFF=10e11 VON=0.01 VOFF=0) C2 8 5 10.9n IC=0 R2 8 5 1e8 .ENDS NOTE some Spice versions (E.G. NGSPICE) use different syntax for the switches: Sdiode 7 1 1 5 Sfb1 ON Scap 8 1 5 1 Sfb2 Off .MODEL Sfb1 SW (RON=0.1 ROFF=10e11 VT=0 VH=-0.01) .MODEL Sfb2 SW (RON=0.1 ROFF=10e11 VT=0.01 VH=0) Analog Power Confidential Analog Power Spice Example (no switch, L3) * Analog Power Spice Level 3 Model - fixed temperature * Rev 4/14/2014 PD * Level 3 model is experimental, sub-threshold leakage is overestimated, which will affect VSD diode modeling .SUBCKT AM3446N 1 2 3 *Nom Temp=25 deg C Mos1 4 5 6 6 APLMOS l=0.25u w=1 .MODEL APLMOS NMOS (LEVEL = 3 vto=0.91 KP =10u NSUB=2e+17 Kappa = 0.12 CGDO = 55p CGSO = 336p) Rdrain 1 4 28m Dbody 6 1 BodyD .MODEL BodyD D (IS=0.5e-12 RS=30e-3 CJO=10p M=0.2) Lsource 3 6 0.3e-9 Rgate 2 5 3 Dcgd 5 7 Crss .MODEL Crss D (RS=1e-3 CJO=400p M=0.91) B1 7 1 V= (abs(v(5)-V(1))+(v(5)-V(1)))/2 C2 8 5 400p IC=0 R2 8 5 1e9 B2 1 8 V= (abs(v(1)-V(5))+(v(1)-V(5)))/2 .ENDS Analog Power Confidential Level 1 and Level 3 Models • Many vendors add many external components and use more complicated BSIM models, but do they work any better? • Parameter-derived level 1 model is recognized as suitable for discrete devices for modeling switching time etc – more complicated models are intended for use in IC modeling and are process-derived • However level 1 model does not model RDS variation with VGS well for modern devices and switching characteristics may suffer – Use Analog Power Level 3 model instead • Analog Power models are device derived, as opposed to process and theory derived and therefore more accurate • Rather than include temperature dependencies, our simple model can be accurately tweaked for any temperate and this provides a faster iteration to modeling at higher temperatures Analog Power Confidential Transfer Characteristics • Level 1 model uses simple equation: ID α (VGS – VGS(TH))2 • This model holds true for state of the art Trench MOSFETs, especially surface mount where current density is quite low • KP (Spice model parameter) easy to derive from characterization data. L1 model gives accurate transfer function, but inaccurate RDS VS VGS plot • Level 3 model allows KP to reflect accurate RDS VDS VGS yet still provides accurate Transfer characteristics Analog Power Confidential CRSS – The key to accuracy Three components: • CGDO – part of level 1 model – • • does not vary with VDS Reverse biased diode – gives variation with VDS – removed when VGD>0 Fixed CDG2 capacitor – switched in when VGD>0 – 1.2 X value of diode at VDG = 0 to reflect higher CRSS for +ve VGD • The combination of a diode with fixed parallel capacitance gives fit with data • Alternate implementation with voltage sources works in identical manner, but use of switches is avoided – simplifies syntax, and avoids SPICE transients Analog Power Confidential Comparison Data Sheet Vs. Model 25000 Capacitance (pF) 20000 15000 10000 5000 0 0 5 10 CISS Data sheet COSS 15 CRSS 20 VDS (V) Model Analog Power Confidential Conclusion Analog Power proposed SPICE subcircuit: • Simple and therefore fast, no switches, no extra active components • Device derived. Accurate in operation (switching, RDS) • L3: Developed predominantly for optimum part selection in PWM applications – L1 most accurate for linear regulator type aplications • Device-derived and therefore contains accurate parameters • Easily adjusted to any operating temperature • Allows what-if experiments, parameters are easily identifiable and editable • L3 model includes accurate transfer AND RDS Vs VGS modeling Analog Power Confidential

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