|
University of California Berkeley EE 141 Spring 2008 Laboratory Exercise 4 Schematic and Layout Simulation Exercise |
|
The objective of this laboratory exercise is to walk you through the process of simulating a schematic and building its layout using previously created components.
At the end of this laboratory exercise, you should be able to: · Create a layout using instances of existing layout blocks. · Simulate the extracted schematic.
Deliverables for this laboratory exercise: Due at the end of the laboratory session. · Printout of the post-layout simulation results for CMOS ring oscillator including the transient response, oscillation frequency and average power.
I. Creating the CMOS Ring Oscillator Schematic
Create a new schematic of a 5-stage CMOS ring oscillator, similar to the one shown below. Use the inverters you created for HW1 and create an output pin RingOut (any convenient node will do).
Similar to HW1, create a symbol view of your ring oscillator. Next, create a top-level schematic containing your ring oscillator symbol and the vdc component that provides the supply voltage similar to the one below.
Note that to prevent any unconnected warnings, add the noConn symbol to the RingOut output pin. You can instantiate the noConn from the basic library as shown below.
II. Simulating the CMOS Ring Oscillator Schematic
Start the simulator using Tools → Analog Environment from the menu bar. In this exercise, we will use the AWD waveform viewer and calculator. Select Session → Options from the Analog Design Environment menu bar and set the options similar to the one below:
Next, copy the variables in the schematic into the simulator by clicking Variables → Copy From Cellview in the Analog Design Environment menu bar. The variable VDD should appear in the Design Variables section of the Analog Design Environment window.
Fill in the value of the variable VDD by clicking Variables → Edit… from the menu bar and fill in the Editing Design Variables form as shown below.
To set the transient simulation options, click Analyses → Choose… from the menu bar and fill out the transient analysis form as shown below.
To make sure that your ring oscillator oscillates, instead of just staying in a metastable state, you need to set the initial state of the output node. To do this, click on Simulation → Convergence Aids → Initial Condition… on the Analog Design Environment menu bar. The Select Initial Condition Set window will appear. Selecting the RingOut node will set its initial condition to the default 0V.
To be able to view the current drawn from the supply, click on Outputs → To Be Saved → Select On Schematic and select the negative terminal of the DC supply. Your Analog Design Environment window should look similar to the one below.
To run the simulation, click on Simulation → Netlist and Run. To view the results when the simulator finishes, click on Results → Direct Plot → Transient Signal then click on the RingOut node on the schematic. Press ESC to view the waveform. It should look similar to the one below:
We will be adding sub-windows to this window to view both the frequency and power of the ring oscillator as calculated from the simulation results. Click on the Add Subwindow icon (the bottom-most icon on the toolbar on the left-hand side of the Waveform Window) to create a sub-window.
Click on the Calculator icon (the 3rd icon from the bottom on the toolbar on the left-hand side of the Waveform Window) to bring up the Calculator, shown below.
Make sure that you enable the new sub-window you created by clicking on it once and enter frequency(VT(“/RingOut”)) into the Calculator window similar to the one below.
|
|
UC Berkeley EE 141 Spring 2008 Last modified: 2/19/2008 12:42 AM by Louis Alarcon |