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Hspice TUTORIAL

By Admin on

Your first hspice program


Let us take a look at the following hspice code. 


* Stripline circuit
.Tran 50ps 7.5ns
.OPTION post Probe
VIN 1 0 PWL 0 0v 250ps 0v 350ps 3.3v
Rsource 1 2 50
Tfirst 2 0 3 0 ZO=50 TD=0.17ns
*C2 3 0 2p
Tsecond 3 0 4 0 ZO=50 TD=500ps
Rtermination 4 0 50
.Probe v(1) v(2) v(3) v(4)
.End



Let us understand the elements of the code of hspice. The statement 


* Stripline circuit 


is a comment in hspice. Any line starting with * is taken as a comment. Use comments profusely to make your code more understandable. 


The statement 


.Tran 50ps 7.5ns 


instructs hspice simulator to perform transient simulation analysis up to time period 7.5ns. 


The statement 


VIN 1 0 PWL 0 0v 250ps 0v 350ps 3.3v 


Creates a piecewise linear voltage source. The voltage source is connected between nets named 1 and 0. The net 0 or GND is universally reserved for ground. At time t = 0, the level of voltage is 0v. At time t = 250 ps, the voltage level is 0v. At time t = 350 ps, the voltage level is 3.3v. This creates a voltage source with 0% to 100% rise time of 100 ps. The voltage rises between time 250 ps to 350 ps. 


The statement 


Rsource 1 2 50 


connects a resistance of 50 ohm between net node 1 and net node 2. We therefore, have a voltage source with 50 ohm source resistance. 


The statement 


Tfirst 2 0 3 0 ZO=50 TD=0.17ns 


Creates a transmission line connected between net node 2 and net node 3. The transmission line has a impedance of 50 ohms and delay of 0.17ns. 


The statement 


*C2 3 0 2p 


is a comment. Had there been no * in the beginning it would have inserted a 2pf capacitor between net node 3 and ground. 


The statement 


Tsecond 3 0 4 0 ZO=50 TD=500ps 


Again creates a transmission line of characteristic impedance 50 Ohms and length equivalent to a delay time of 500 ps. 


We place a termination resistance of 50 Ohms, using the statement 


Rtermination 4 0 50 


Finally the statement 


.Probe v(1) v(2) v(3) v(4) 


is used to probe the voltage levels at nodes 1, 2, 3 and 4. 

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