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Design Languages >> Verilog-AMS >> How do I generate the following voltage profile?
https://designers-guide.org/forum/YaBB.pl?num=1453259912

Message started by Rosh on Jan 19^th, 2016, 7:18pm

Title: How do I generate the following voltage profile?
Post by Rosh on Jan 19^th, 2016, 7:18pm

Hi everyone,

I am trying to generate the following voltage profile.

Picture attached.

http://imgur.com/141W8kp

The specifications are :
Vhigh: Voltage 1
Tr: Rise time
Vlow: Voltage 2
Time: Time after which Vhigh falls to Vlow
Tf: Fall time

Code:

`include "disciplines.vams"

module series_rlc1 (p, n1);

parameter real r=1,vout_high=5, //VHIGH value
trise = 100u, //Fall Time
tfall = 100u, //Rise Time
vout_low=3, //VLOW Value
droop_time=3000u;//Time after which VHIGH falls to VLOW

inout p, n1;
electrical p, n1;

analog begin

V(n1) <+ transition(vout_high,0,trise,tfall);

if($abstime==droop_time)
V(n1) <+ transition(vout_low,0,trise,tfall);

end
endmodule

However, I get an error saying I cannot include a transition operator inside a conditional statement. So how do I tell the compile to drop the voltage after a time?

Title: Re: How do I generate the following voltage profile?
Post by Geoffrey_Coram on Jan 20^th, 2016, 8:05am

I think you are missing some basic understanding of how the Verilog-A contribution operator works. The code you posted would set the voltage on "n1" to vout_high for all time *except* for the timepoint exactly at droop_time.

I think the code below will work better.

Code:

`include "disciplines.vams"

module series_rlc1 (p, n1);

parameter real r=1,vout_high=5, //VHIGH value
trise = 100u, //Fall Time
tfall = 100u, //Rise Time
vout_low=3, //VLOW Value
droop_time=3000u;//Time after which VHIGH falls to VLOW

inout p, n1;
electrical p, n1;

real vout;

analog begin
@(initial_step) begin
vout = vout_high;
end
if($abstime>=droop_time) begin
vout = vout_low;
end

V(n1) <+ transition(vout,0,trise,tfall);
end
endmodule

However, I get an error saying I cannot include a transition operator inside a conditional statement. So how do I tell the compile to drop the voltage after a time?[/quote]