sigma delta verilog model
module firstorder_sigmadelta(in,clk,out);
input in,clk;
output out;
voltage in,clk,out;
parameter real quantizer_vth=0.0;
parameter real clk_vth=2.5;
parameter real d2a_gain=5.0;
real vsum;
real vd;
real vint;
real vout;
real hi,lo;
analog
begin
@(initial_step)
begin
vd=0;vint=0;vout=0;
hi = 1; lo = -1;
end
@(cross(V(clk) – clk_vth,1))
begin
// summing junction
vsum = V(in) – vd ;
// integrator
vint = vint + vsum;
// quantizer
if (vint > quantizer_vth) vout = hi ;
else vout = lo ;
// D to A
vd = d2a_gain*vout ;
end
V(out) <+ vout ;
end
endmodule