The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design Languages >> Verilog-AMS >> simulating .va files in hspice
https://designers-guide.org/forum/YaBB.pl?num=1552848227

Message started by masoumeh on Mar 17^th, 2019, 11:43am

Title: simulating .va files in hspice
Post by masoumeh on Mar 17^th, 2019, 11:43am

Hi
I'm working on simulating an ideal delta sigma modulator in hspice and I need to use ideal models for different parts of my circuit. for example I want to simulate the quantizer.va model in hspice for a 3rd level quantizer. I follow the manual for simulating this kind of models in hspice but unfortunately it is not working. I will appreciate if anyone can help me.
the .va and .sp files are attached below and are written too.
Also the problem is that when I simulate the test.sp in hspice nothing happen and the .lis file is empty and no error and other information is shown.
.

quantizer.va file:

// N-level triggered quantizer (like an ADC followed by a DAC)
//
// Version 1b, 17 July 03
//
// Ken Kundert
//
// Downloaded from The Designer's Guide (www.designers-guide.org).
// Post any questions to www.designers-guide.org/Forum

`include "disciplines.vams"

module quantizer (out, in, clk);

output out; voltage out;// output
input in; voltage in; // input
input clk; voltage clk; // clock input (edge triggered)
parameter integer levels=2 from [2:inf);// number of quantization levels
parameter real vh = +1; // voltage of highest level
parameter real vl = -1 from (-inf:vh); // voltage of lowest level
parameter real vth = (vh + vl)/2; // threshold voltage of clock
parameter integer dir = +1 from [-1:+1] exclude 0;
// if dir=+1, rising clock edge triggers
// if dir=-1, falling clock edge triggers
parameter real td = 0 from [0:inf); // output delay
parameter real tt = 0 from [0:inf); // output transition time
real quantized, delta;
integer level;

analog begin
@(cross(V(clk) - vth, dir) or initial_step) begin
delta = (vh-vl)/(levels-1);
level = (V(in)-vl)/delta;
if (level < 0)
level = 0;
else if (level >= levels)
level = levels-1;
quantized = level * delta + vl;
end
V(out) <+ transition( quantized, td, tt );
end
endmodule

test.sp file:

Title: testing verilog-A
.hdl quantizer.va
.options post=1

VCLK clk 0 pulse 0 1 1f 1f 1f 0.390625u 0.78125u
Vin in 0 SIN 0 1 2k

Xquantizer1 out in clk quantizer levels=3 vh=1 vl=-1 vth =0 dir=1 td=0 tt=0
RL out 0 1meg

.option method=gear post=1
.options delmax=10n
.temp 25
.op
.tran 10n 20m

.end

Title: Re: simulating .va files in hspice
Post by Ken Kundert on Mar 17^th, 2019, 3:12pm

If you want help, it is probably best to simply show the .va and .sp files rather than force people to download and unpack them. Also, you should give the error message or at least describe what is going wrong.

The way it currently stands, you are expecting people to do a bunch of work before they have any indication as to whether they can help you or not.

Title: Re: simulating .va files in hspice
Post by masoumeh on Mar 17^th, 2019, 3:31pm

Thank you for your comment, I edited the post.

Title: Re: simulating .va files in hspice
Post by Andrew Beckett on Mar 18^th, 2019, 7:18am

The main issue is that you have vth=0 on the instance line for the quantizer, and since the clock transitions between 0 and 1V, it never crosses the threshold. Set it to 0.5 instead.

You also have your rise, fall and delay for the clock source set to the ridiculously short 1fs. That is going to make the simulator slower by trying to follow these unrealistically short transition times. Similarly you should set tt on the quantizer instance to be greater than 0. So I would suggest:

Code:

VCLK clk 0 pulse 0 1 100p 100p 100p 0.390625u 0.78125u

Xquantizer1 out in clk quantizer levels=3 vh=1 vl=-1 vth =0.5 dir=1 td=0 tt=100p

I ran this in spectre (with the same netlist) and it then works fine. Even 100ps rise time/transition may be shorter than you really need if you've got a 1.28MHz clock. That said, for spectre it didn't affect the speed that much between 100p or 1n.

Andrew.