Simulation in spectre(S) using the Affirma Environment

This tutorial explains how to simulate your circuit, in this case inverter using Affirma Environment.

To simulate inverter, you need to create test schematic that has cell name of INV_TB in library of EE525.
It will have a inverter, power supply, input source, and a ground to test its transient response.
Add the symbol of inverter you made, power supply, capacitor, and input source according to Figure 14. And just repeat tutorial of Schematic Entry with Composer.  
 


adding cap         adding inv


adding pulse      adding power
 Figure 14. Adding symbols of inverter, load capacitor, power supply and input source 
 


Press the Esc key to get out of Add Instance mode and wiring the schematic like Figure 15.


completed test circuit
Figure 15. The completed test circuit



Don't forget to save by selecting Design --> Check and Save in Composer-Schematic menu.


To simulate your circuit, in this case INV_TB

1. From Composer-Schematic menu, select Tools --> Analog Environment.   This brings out Affirma Environment window as Figure 16.


Affirma Env
Figure 16. Affirma Analog Environment



2. In Affirma Environment window, select Setup --> Simulator/Directory/Host ...  A Choosing Simulator/Directory/Host window appears like Figure 17.
    Make sure the simulator is set to SpectreS. Click on OK when you are done.
 

setting simulator
Figure 17. Setting up the simulator



3. In Affirma Environment window, select Setup --> Model Path... A Setting Model Path window appears.
    Type /usr/local/cadence/NCSU/local/models/spectre/nom in New Directory. Click Add above and you will have same window as Figure 18.


setting up model path
Figure 18. Setting up the model path



4. Then, in Affirma Environment window, select Analyses --> Choose... and fill it out according to Figure 19.


setting up analysis
Figure 19. Setting up transient analysis



5. In Affirma Environment window, select Ouptuts --> To Be Plotted --> Select On Schematic.
   Then, go back to schematic and click on the wires attached  input and output of inverter. The wires should change colors.
   Press Esc key to exit of selection mode. The signals should be added in the outputs window, as Figure 20.


ready for simluaiotn
Figure 20. Affirma Environment ready for a simulation



6. In Affirma Environment window, select Simulation --> Run. The plot of the simulation should appears in Waveform Window , like Figure 21.
    To measure low to high propagation delay, go to Markers --> Crosshair Marker A, Crosshair Marker B and place it at the 2.5V position on the input source
    according to Figure 21. You have 1.62ns of delay.


  simulation result
  Figure 21. Simulation result



7. To save your simulation conditions, in Affirma Environment window, select Session --> Save State..., then OK.

8. Exit Affirma Environment and Composer-Schematic window.








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