I have developed Verilog-A model of a device that I am trying to simulate and every time it gives different value and at most of the occasions it just stops at a certain time of the simulation.
I have seen multiple posts around the same issue and it seems that this is due to a bad Verilog-A model or varying a bit the convergence parameters.
I would like to get your suggestions of either updating the model or changing the convergence parameters in a matter to get this module working properly.
The model is as follows;
//Start
`resetall
`include "constants.vams"
`include "disciplines.vams"
// check this for later updates//////////////////////////////
nature Magnetization
access = Mgn;
units = "SI";
abstol = 1;
endnature
nature Ange
access = Ang;
units = "rad";
abstol = 1;
endnature
discipline magnetization
potential Magnetization;
enddiscipline
discipline ange
potential Ange;
enddiscipline
/////////////////////////////////////////////////////////////
//Constants
//Define various physical constants in SI units
`define Pi 3.141592653589793 //rad
//`define m_Bohr 9.27401E-24 // J/T Bohr Magneton
//`define h 6.626070040E-34 // J.s Plank's constant
`define hbar 1.054571800e-34 // J.s Reduced Planck's constant
//`define eV 1.60217653E-19 // C Electron charge
`define KB 1.38064852E-23 // J/K Boltzman constant
`define mu0 1.256637061435917E-06 // N/A^2 Permeability of free space
//`define ep0 8.854187817620389E-12 // F/m Permativity of free space
`define e 1.60217653E-19 // C Electron charge
//`define me 9.1093826E-31 // Kg Electron rest mass
//`define a0 5.29177E-11 // m Bohr radius
module asdw(T1,T2,R_out1,R_out2);
/*-------T1~2: Actual terminals coressponding to pinned layer and free layer--------*/
inout T1,T2;
electrical T1,T2;
/*-------Tmz: Virtual terminal for monitoring the Magnetization-------*/
output R_out1,R_out2;
electrical R_out1,R_out2;
// magnetization Tmx,Tmy,Tmz;
ange Th1, Ph1;
ange Th2, Ph2;
///////////////////////////////////////////////////////////////////////////////////////////
/* Simulation time step bound */
///////////////////////////////////////////////////////////////////////////////////////////
parameter real Ts = 2p; // Speed-accuracy tradeoff
parameter integer TN = 0;
///////////////////////////////////////////////////////////////////////////////////////////
/* TN is a model parameter to enable Thermal fluctuations */
/* TN = 1 : Thermal fluctuations is activated */
/* TN = 0 : Thermal fluctuations is NOT activated */
///////////////////////////////////////////////////////////////////////////////////////////
// parameter integer STT = 0;
///////////////////////////////////////////////////////////////////////////////////////////
/* JH is a model parameter */
/* JH = 1 : Joule heating mechanism is activated */
/* JH = 0 : Joule heating mechanism is NOT activated */
///////////////////////////////////////////////////////////////////////////////////////////
// parameter integer JH = 0;
///////////////////////////////////////////////////////////////////////////////////////////
/* SHAPE is a model parameter */
/* SHAPE = 1 : MTJ cross section is circular */
/* SHAPE = 0 : MTJ cross section is rectangular */
///////////////////////////////////////////////////////////////////////////////////////////
// parameter integer SHAPE = 1;
///////////////////////////////////////////////////////////////////////////////////////////
/* Device parameters */
///////////////////////////////////////////////////////////////////////////////////////////
// parameter real Ms0 = 8E5;
parameter real Ms0 = 1.2E6;
// parameter real alpha1 = 0.01;
parameter real alpha1 = 0.02;
parameter real gamma = 2.21276E5;
///////////////////////////////////////////////////////////////////////////////////////
/* Device size */
///////////////////////////////////////////////////////////////////////////////////////
// parameter real t_FL = 2e-9; /
parameter real t_FL = 1.1E-9;
// parameter real w_FL = 70e-9; //
parameter real w_FL1 = 170E-9; //
// parameter real l_FL = 140e-9; // (
parameter real l_FL1 = 60E-9; // (
parameter real w_FL2 = 170E-9; //
// parameter real l_FL = 140e-9; //
parameter real l_FL2 = 60E-9; // (m)
// parameter real t_ox = 0.8e-9; // (m)
parameter real t_ox = 1.1E-9; // (m)
///////////////////////////////////////////////////////////////////////////////////////
/* Magnetoresistance and electrical parameters */
///////////////////////////////////////////////////////////////////////////////////////
// parameter real b_h = 3.28; //ev
parameter real b_h = 0.39; //ev
// parameter real v_h = 0.75; //V
parameter real v_h = 0.75; //V
parameter real alpha_sd = 1.4e-5; // K^(-3/2)
parameter real P01 = 0.591; //59.1%
parameter real P02 = 0.591; //59.1%
parameter real S = 1.5e-12; //(ohm.(um)^2)^-1 . K^(-4/3)
parameter real TMR0 = 1.5; // TMR @ zero voltage
///////////////////////////////////////////////////////////////////////////////////////
/* Effective field parameters */
///////////////////////////////////////////////////////////////////////////////////////
// parameter real Ki0 = 2.6E5 * t_FL * 0.1; //0.32e-3 //
parameter real Ki0 = 0; //0.32e-3 //(J/m^2) v=0
parameter real eta_VCMA = 0; // J/(V.m)
//External Field
parameter real hx_external= 0; //-31830 A/m external magnetic field along x axis
parameter real hy_external= 0; // A/m mexternal magnetic field along y axis
parameter real hz_external= 0; // A/m external magnetic field along z axis
//Demagnetization Fields, Shape anistropy field
// parameter real Nx= 0.018;//0.0168 X-axis component of the demagnetization facator
// parameter real Ny= 0.038;//0.0168; Y-axis component of the demagnetization facator
// parameter real Nz= 0.94;//0.9664; Z-axis component of the demagnetization facator
parameter real Nx= 0.0045;//0.0168 X-axis component of the demagnetization facator
parameter real Ny= 0.0152;//0.0168; Y-axis component of the demagnetization facator
parameter real Nz= 0.9803;//0.9664; Z-axis component of the demagnetization facator
//////////////////////////////////////////////////////////////////////////////////////////
/* Spin Transfer Torque Parameters */
///////////////////////////////////////////////////////////////////////////////////////
parameter real th_initial1= `Pi/2; // Azimuth initial angle (with Z direction)
// parameter real ph_initial1= 0.001; // Elevation angle (with X direction in X-Y plane)
parameter real ph_initial1= `Pi-0.1; // Elevation angle (with X direction in X-Y plane)
parameter real th_initial2= `Pi/2; // Azimuth initial angle (with Z direction)
// parameter real ph_initia2= 0.001; // Elevation angle (with X direction in X-Y plane)
parameter real ph_initial2= `Pi-0.1; // Elevation angle (with X direction in X-Y plane)
// parameter real pin_x= 0; // pinned layer orientation
// parameter real pin_y=0; // pinned layer orientation
// parameter real pin_z=1; // pinned layer orientation
parameter real pin_x= 1; // pinned layer orientation
parameter real pin_y=0; // pinned layer orientation
parameter real pin_z=0; // pinned layer orientation
// parameter real zeta= 1;//%0.58; // Spin polarized percent STT Coefficent
// parameter real zeta_FL= 0; // Field-like STT torque coefficient
parameter real zeta_FL= 1;//%0.58; // Spin polarized percent STT Coefficent
parameter real zeta_DL= 0; // Field-like STT torque coefficient
integer seed;
parameter real Ta = 300; // Ambient temperature (K)
///////////////////////////////////////////////////////////////////////////////////////
// Model computing parameters: //
///////////////////////////////////////////////////////////////////////////////////////
real gamma_llg, surface1, surface2,volume1,volume2;
real H_Demx1, H_Demy1, H_Demz1,H_Demx2, H_Demy2, H_Demz2;
real Hkp1,Hkp2;
real H_effx1, H_effy1, H_effz1,H_effx2, H_effy2, H_effz2;
real Hlx1, Hly1, Hlz1,Hlx2, Hly2, Hlz2, Temp, Q1,Q2;
real AJ1, BJ1,AJ2, BJ2;
// real AJ_polarizer, BJ_polarizer;
real st1, ct1, sp1, cp1,st2, ct2, sp2, cp2;
real Heff_spherical_theta1, Heff_spherical_phi1, dMdt_eff_theta1, dMdt_eff_phi1;
real Heff_spherical_theta2, Heff_spherical_phi2, dMdt_eff_theta2, dMdt_eff_phi2;
real T_STT_spherical_pinned_theta1, T_STT_spherical_pinned_phi1, dMdt_STT_pinned_theta1, dMdt_STT_pinned_phi1;
real T_STT_spherical_pinned_theta2, T_STT_spherical_pinned_phi2, dMdt_STT_pinned_theta2, dMdt_STT_pinned_phi2;
// real T_STT_spherical_polarizer_theta, T_STT_spherical_polarizer_phi, dMdt_STT_polarizer_theta, dMdt_STT_polarizer_phi;
real dMdt_theta1, dMdt_phi1,dMdt_theta2, dMdt_phi2;
real M_theta1, M_phi1, M_theta2, M_phi2;
real I_STT,R1,R2;
real TD,Time1,Time2;
real C,sin_temp,G_T1,G_T2, G_V, G_SI, P1_T, P2_T, G1,G2;
real t_ox_angestrom,C0,C1,C2,A_cm2_1,A_cm2_2,G01,G02,TMR_mod,F;
///////////////////////////////////////////////////////////////////////////////////////
/* Branches */
///////////////////////////////////////////////////////////////////////////////////////
// branch (T1,T2) res_mtj;
///////////////////////////////////////////////////////////////////////////////////////
/* Main */
///////////////////////////////////////////////////////////////////////////////////////
analog begin
$bound_step(Ts); // define simuation time step
@(initial_step) begin
M_theta1= th_initial1;
M_phi1=ph_initial1;
M_theta2=th_initial2;
M_phi2=ph_initial2;
seed = 25;
//T1 = 0;
F=1;
t_ox_angestrom =t_ox*1e10;
surface1 = `Pi*l_FL1*w_FL1/4; // (m^2) Surface area
surface2 = `Pi*l_FL2*w_FL2/4; // (m^2) Surface area
volume1 = surface1*t_FL; // (m^3) Surface area
volume2 = surface2*t_FL; // (m^3) Surface area
gamma_llg = gamma/(1+alpha1*alpha1); // Hz/T (1/T.m) Reduced gyromagnetic ratio
A_cm2_1 = surface1*1e4;
A_cm2_2 = surface2*1e4;
G01 = ((3.16*1e10)*sqrt(b_h)/t_ox_angestrom) * exp(-1.025 * t_ox_angestrom * sqrt(b_h)) * A_cm2_1 * F; // 1/ohm
G02 = ((3.16*1e10)*sqrt(b_h)/t_ox_angestrom) * exp(-1.025 * t_ox_angestrom * sqrt(b_h)) * A_cm2_2 * F; // 1/ohm
// G0=2.77414e-4; //(APPLY kAZ PARAMETERS)
end
Time2 = $abstime;
TD = Time2 - Time1; //Time duration
Time1 = Time2;
Temp = Ta;
if (TN == 1)
begin
Q1 = sqrt((2 * alpha1 * `KB * Temp / (`mu0*gamma_llg * Ms0 * volume1 * TD)));
Q2 = sqrt((2 * alpha1 * `KB * Temp / (`mu0*gamma_llg * Ms0 * volume2 * TD)));
end
else
begin
Q1 = 0;
Q2 = 0;
end
Hlx1 = $rdist_normal(seed,0,Q1); //$dist_normal (seed, mean, standard_deviation) ; seed const means get const random value
Hly1 = $rdist_normal(seed,0,Q1);
Hlz1 = $rdist_normal(seed,0,Q1);
Hlx2 = $rdist_normal(seed,0,Q2); //$dist_normal (seed, mean, standard_deviation) ; seed const means get const random value
Hly2 = $rdist_normal(seed,0,Q2);
Hlz2 = $rdist_normal(seed,0,Q2);
st1 = sin(Ang(Th1));
ct1 = cos(Ang(Th1));
sp1 = sin(Ang(Ph1));
cp1 = cos(Ang(Ph1));
st2 = sin(Ang(Th2));
ct2 = cos(Ang(Th2));
sp2 = sin(Ang(Ph2));
cp2 = cos(Ang(Ph2));
// as H_dem = - Ms (N(vector).M(vector) (Nx,Ny,Nz). (M_theta,Mphi) cross product
H_Demx1= Nx*Ms0 * st1 * cp1 ;
H_Demy1= Ny*Ms0 * st1 * sp1;
H_Demz1= Nz*Ms0 * ct1;
H_Demx2= Nx*Ms0 * st1 * cp1 ;
H_Demy2= Ny*Ms0 * st1 * sp1;
H_Demz2= Nz*Ms0 * ct1;
//Anisotropy Field, Interfacial
Hkp1= (2*Ki0/(t_FL*`mu0*Ms0)-2*eta_VCMA*V(T1,T2)/(t_FL*`mu0*Ms0*t_ox))*ct1; // The effective anistropy with VCMA effect
Hkp2= (2*Ki0/(t_FL*`mu0*Ms0)-2*eta_VCMA*V(T1,T2)/(t_FL*`mu0*Ms0*t_ox))*ct2; // The effective anistropy with VCMA effect
//Effective anistropy field with VCMA
H_effx1= Hlx1 + hx_external- H_Demx1;
H_effy1= Hly1 + hy_external- H_Demy1;
H_effz1= Hlz1 + hz_external- H_Demz1 + Hkp1;
H_effx2= Hlx2 + hx_external- H_Demx2;
H_effy2= Hly2 + hy_external- H_Demy2;
H_effz2= Hlz2 + hz_external- H_Demz2 + Hkp2;
// write disturbance
//Spin Transfer Torque components
AJ1= (`hbar*zeta_FL*I(T1,T2)/(2*`e*`mu0*Ms0*surface1*t_FL)); //0; %0.3e4; //A/m STT coefficient Normalized
BJ1= (`hbar*zeta_DL*I(T1,T2)/(2*`e*`mu0*Ms0*surface1*t_FL)); // Normalized
AJ2= (`hbar*zeta_FL*I(T1,T2)/(2*`e*`mu0*Ms0*surface2*t_FL)); //0; %0.3e4; //A/m STT coefficient Normalized
BJ2= (`hbar*zeta_DL*I(T1,T2)/(2*`e*`mu0*Ms0*surface2*t_FL)); // Normalized
//
T_STT_spherical_pinned_theta1= pin_x * ct1 * cp1 + pin_y * ct1 * sp1 - pin_z * st1;
T_STT_spherical_pinned_phi1= -pin_x * sp1 + pin_y * cp1;
T_STT_spherical_pinned_theta2= pin_x * ct2 * cp2 + pin_y * ct2 * sp2 - pin_z * st2;
T_STT_spherical_pinned_phi2= -pin_x * sp2 + pin_y * cp2;
// Heff_spherical = @(t,M) [cos(M(1)).* cos(M(2)), cos(M(1)).*sin(M(2)), -sin(M(1)); -sin(M(2)), cos(M(2)), 0] * H(t,M); %A/m Magnetic Field Strength normalized
Heff_spherical_theta1= H_effx1 * ct1 * cp1 + H_effy1 * ct1 * sp1 - H_effz1 * st1;
Heff_spherical_phi1= -H_effx1 * sp1 + H_effy1 * cp1;
Heff_spherical_theta2= H_effx2 * ct2 * cp2 + H_effy2 * ct2 * sp2 - H_effz2 * st2;
Heff_spherical_phi2= -H_effx2 * sp2 + H_effy2 * cp2;
dMdt_eff_theta1= alpha1 * Heff_spherical_theta1 + Heff_spherical_phi1;
dMdt_eff_phi1= -Heff_spherical_theta1/st1 + alpha1 * Heff_spherical_phi1 / st1;
dMdt_eff_theta2= alpha1 * Heff_spherical_theta2 + Heff_spherical_phi2;
dMdt_eff_phi2= -Heff_spherical_theta2/st2 + alpha1 * Heff_spherical_phi2 / st2;
dMdt_STT_pinned_theta1= (-AJ1 - alpha1 * BJ1) * T_STT_spherical_pinned_theta1 + (alpha1 * AJ1 - BJ1) * T_STT_spherical_pinned_phi1;
dMdt_STT_pinned_phi1= (BJ1 - alpha1 * AJ1) * T_STT_spherical_pinned_theta1/st1 + (- AJ1 - alpha1 * BJ1) * T_STT_spherical_pinned_phi1 / st1;
dMdt_STT_pinned_theta2= (-AJ2 - alpha1 * BJ2) * T_STT_spherical_pinned_theta2 + (alpha1 * AJ2 - BJ2) * T_STT_spherical_pinned_phi2;
dMdt_STT_pinned_phi2= (BJ2 - alpha1 * AJ2) * T_STT_spherical_pinned_theta2/st2 + (- AJ2 - alpha1 * BJ2) * T_STT_spherical_pinned_phi2 / st2;
dMdt_theta1= gamma_llg * (dMdt_eff_theta1 + dMdt_STT_pinned_theta1 );
dMdt_phi1= gamma_llg * (dMdt_eff_phi1 + dMdt_STT_pinned_phi1 );
dMdt_theta2= gamma_llg * (dMdt_eff_theta2 + dMdt_STT_pinned_theta2 );
dMdt_phi2= gamma_llg * (dMdt_eff_phi2 + dMdt_STT_pinned_phi2 );
//idtmod(integrand x, initial condition y0, modulus m, offset b, tolerance) preferable than just idt
M_theta1 = idtmod(dMdt_theta1,th_initial1,2*`Pi);
M_phi1 = idtmod(dMdt_phi1,ph_initial1,2*`Pi);
M_theta2 = idtmod(dMdt_theta2,th_initial2,2*`Pi);
M_phi2 = idtmod(dMdt_phi2,ph_initial2,2*`Pi);
// MTJ resistance
C = 1.387e-4 * t_ox_angestrom/sqrt(b_h); //Check the parameters later
sin_temp = sin(C*Temp);
G_T1 = G01* (C*Temp)/(sin_temp);
G_T2 = G02* (C*Temp)/(sin_temp);
G_SI = S*pow(Temp,(4/3)); //
//Method1
P1_T = P01*(1-alpha_sd*pow(Temp,1.5));
P2_T = P02*(1-alpha_sd*pow(Temp,1.5));
G1 = G_T1*(1+P1_T*P2_T*cp1 + G_SI); //
G2 = G_T2*(1+P1_T*P2_T*cp2 + G_SI); //
R1 = 1 / (G1);
R2 = 1 / (G2);
// I(T1,T2) <+ V(T1,T2)/R;
V(T1,T2) <+ I(T1,T2) * (R1+R2);
V(R_out1) <+ R1;
V(R_out2) <+ R2;
Ang(Th1) <+ M_theta1;
Ang(Ph1) <+ M_phi1;
Ang(Th2) <+ M_theta2;
Ang(Ph2) <+ M_phi2;
//
end // end of analog
endmodule // end of module
the input.scs
simulator lang=spectre
global 0
parameters I=600u
// View name: schematic
I1 (0 Vout) isource dc=I type=dc
I5 (Vout 0 Rout1 Rout2) asdw Ts=2e-12 TN=0 Ms0=1.2e+06 alpha1=0.02 \
gamma=221276 t_FL=1.1e-09 w_FL1=1.7e-07 l_FL1=6e-08 w_FL2=1.5e-07 \
l_FL2=5e-08 t_ox=1.1e-09 b_h=0.39 v_h=0.75 alpha_sd=1.4e-05 \
P01=0.591 P02=0.591 S=1.5e-12 TMR0=1.5 Ki0=0 eta_VCMA=0 \
hx_external=0 hy_external=0 hz_external=0 Nx=0.0045 Ny=0.0152 \
Nz=0.9803 th_initial1=1.5708 ph_initial1=0.1 th_initial2=1.5708 \
ph_initial2=0.1 pin_x=1 pin_y=0 pin_z=0 zeta_FL=1 zeta_DL=0 Ta=300
simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \
tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \
digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \
checklimitdest=psf
tran tran stop=800n param=I param_vec=[0 0 30n 450u 50n 0 70n 600u 100n 0 \
150n -620u 170n 0 200n -630u 250n 0 280n 450u 300n 0 330n -630u 360n \
0] step=100000 write="spectre.ic" writefinal="spectre.fc" \
annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
save I5:T1
saveOptions options save=allpub
ahdl_include "/Directory/asdw/veriloga/veriloga.va"
The circuit
