1.1 Create a directory under your home for the VLSI class and keep all of your work in there:2. Simulate the transient response of the inverter>> mkdir egre533Be sure and change into this directory after you login and before you create any new designs for this class.
>> cd egre5331.2 Create a directory for this lab and move into it. Then start Design Architect, IC version (DAIC):
>> mkdir lab11.3 In DAIC open a sheet called inv and click on the ADK IC Library item in the palette to bring up the library of transistors that you will use to develop your IC cells. Use your knowledge of DAIC to create a schematic of an inverter using PMOS and NMOS devices, VDD, GND, and portin and portout components. Don't forget to connect the body contacts of the transistors and change the width of the PMOS device to 10 from the default. The resulting schematic should look like the one below:
>> cd lab1
>> adk_daic &
1.4 Check and save the sheet, fixing any errors then exit DAIC.
2.1 Setup the simluator itself by selecting the Session button under Setup. You will need to setup three dialogue boxes under this item. First choose the Simulator/Viewer option. Make the resulting dialogue box look like the one shown below and click OK. Do not change the Advanced Options - they are set correctly by default.
2.2 Next select the Netlister option from the Session button under Setup. Make it look as shown then click OK. Be sure to enter GND beside the Set Node 0 box - this informs the simulator thatGNDis voltage ground (0 Volts).
2.3 Finally select the Environment option from the Session button under Setup. Make it look as shown then click OK.
2.4 Setup the simulator to use the AMI05 process models by left clicking the Lib/Temp/Inc button under Setup. Then choose the Libraries option. Use the Browse button to navigate to the ami05 model as shown. The ami05 model file is located at /mentor/adk3_0/technology/ic/models. You must setup the supply voltage because the ADK allows designs to be created for 2.5V, 3.3V and 5V logic. Your design in the ami05 process will use a 5 Volt supply. Specify VDD = +5V by setting the second Library Path to the VDD_5 file as shown then click OK.
2.5 Setup a transient simulation. From the schematic sim palette left click on Analyses under Setup. In the Setup Simulation Analysis dialogue box check the box beside Transient as shown. Left click on the Setup button beside Transient. You will see the Setup Transient Analysis dialogue box. Fill it out as shown then click OK. You have now setup a simulation to perform transient analysis. The simulation will start at time 0 nanoseconds and stop at time 100 nanoseconds. Click OK in the Setup Simulation Analysis dialogue box also.
2.6 Define an input waveform for the inverter. First select the in1 signal on the schematic by left clicking on it. Then select the Forces button on the schematic sim palette. Choose Add from the list of choices. Then complete the dialogue box as shown below. Note the waveform is defined using the PULSE tab in the dialogue box. The other tabs (DC, AC, ...) represent other ways to define forces. Click OK. This will create an input waveform to test your inverter. The input will be a pulse which startss low (0v) at time 0 then pulses high (5v) 25 nanoseconds later and repeats at 50 nanosecond intervals. The rise time and fall time of the pulse will be 1 nanosecond. Since the stop time was set earlier at 100 nanoseconds, you should see two pulses.
2.7 Setup the voltages to be plotted by the simulation. Select the in1 signal on the schematic by left-clicking on it. Then left click on the Probes/Plots button under Setup on the schematic sim palette. Choose Save Selected. Fill in the dialogue box as shown below then click OK. Repeat this procedure to add the out1 signal to the plot.
2.8 Finally, you need to scale the transistor values of L and W to the correct value. For layout, these values are specified in Lambda units. However, for simulation, they need to be expressed in microns. The easiest way to do this is to put a scaling factor for Lamdba into the expression for L and W on each transistor. If you do not do this, you will be simulating the transistors with width and length values expressed in whole microns and you will not get the correct results!
Place the cursor over the value of 2 for L on the PMOS transistor and hit the <shift>< and F7> keys simultaneously. A dialog box like the one below will open up:
Mover the cursor over the New Value item and change the value of 2 to 2*0.3 (Lambda for the AMI 0.5 process is 0.3 microns). Place the cursor over the Type item and change it to expression. The dialog box will now look like this:
Hit the OK button on the dialog box. The new value for the L of the PMOS transistor will be calculated and placed on the schematic. The resulting schematic will look like the one below:
In a similar manner, change the values of the W parameter on the PMOS to 5*0.3, and the L and W parameters on the NMOS to 2*0.3 and 5*0.3 respectively. The schematic will now look like the one below:
You can now run the simulation and get the correct results for the devices sized to the AMI 0.5 process.
Note that when you want to change the dimensions of the transistors to balance them, you will do this by changing the value of the multiplier in the expression for W, not by changing the value of lambda. For example, to make the PMOS transistor twice as wide as it is now, you would follow the procedure above and change the value of W to 10*0.3.
2.9 Run the simulation by left clicking the Run ELDO button under Execute on the schematic sim palette (ELDO is the name of the simulator). You will see two text windows open, display results then close as the simulation progresses. Your results should appear as shown below. If you do not see the waveforms shown below after a few seconds then left click on the ASCII Files button under the Results section and choose View Log. This will open a notepad window containing the log file for your simulation. You can read the log file to locate your errors. When you have finished reading the log file, close notepad by left clicking twice in the top right corner of the window. Correct your errors and run the simulation again.
2.10 Select File->Print from the EZwave window to print your simulation results. Then close the EZ-wave viewer by left clicking once in the top left corner of the EZ-wave window and selecting Close.
Now you will change the simulation to simulate the DC switching characteristics of the inverter. You will program the simulator to sweep the input voltage from 0V to 5V and plot the resulting output voltage. This plot of VOUT vs. VIN will show the switching threshold and noise margin for your design. You will need to delete the FORCE and PROBES from the previous exercise and setup a DC analysis instead of a transient analysis.3.1 Delete the previous FORCE by left clicking on the Forces button under Setup then choosing Edit/Delete/Show. Select the force in the dialogue box by left clicking once on it then left click on the Delete Selected button. The force should be erased. Then left click on the Exit button.
3.2 Delete the previous PROBES by left clicking on the Probes/Plots button under Setup then choosing Edit. Select then delete each entry by first left clicking once on the entry to select it then left clicking on the Delete button to delete it. When you have deleted all probes from the previous exercise then left click the OK button.
3.3 Add a DC force to the input signal (you will need a DC force to sweep for voltage characteristics) by first selecting the in1 signal in the schematic window. Then left click on the Forces button under Setup and choose Add. Use the DC tab and make the dialogue box look as shown then left click OK. You have defined a DC force necessary for the sweep.
3.4 Left click on the Analyses button under Setup. Uncheck Transient and check DC. Then left click on the Setup button beside DC. Fill out the Setup DC Analysis dialogue box as shown then left click OK. Left click OK in the Setup Simulation Analysis dialogue box also.
3.5 Setup the signals to plot. This time you want both in1 and out1 plotted on the same chart (normal for viewing transfer characteristics). First select in1 by left clicking on it in the schematic window. Next hold down the control key on the keyboard and left click on the out1 signal. Both signals should now be selected (dashed). Now left click on the Probes/Plots button under Setup and choose Save Selected. Mkake sure the resulting dialogue box looks as before (Save Voltage selected, Plot Items checked) then left click on the OK button. This time, since you have specifed more than one signal to plot, the simulator will bring up an additional dialogue box. Fill it out as shown below then left click OK.
3.6 Run the DC sweep by left clicking on the Run ELDO button under Execute. As before, wait for the netlist window then the simulation window to open and close. After a few seconds the waveform window should open and you should see a plot similar to the one below. As before, if you do not get the desired results then left click on the ASCII Files button under Results and choose View Log. Look through the log file to find your errors and correct them.
3.7 Close the EZ wave window. Then select the End Sim button under schematic sim to terminate simulation. Then close your DAIC window.
Based on the tutorial prepared by David Zar.