ECE 3130 – Digital Electronics and Design
description
Transcript of ECE 3130 – Digital Electronics and Design
![Page 1: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/1.jpg)
Allan Guan
ECE 3130 – Digital Electronics and Design
Lab 4VTC and Power Consumption
Fall 2012
![Page 2: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/2.jpg)
Allan Guan
Today’s Lab
• Plot VTC for an inverter• Check if VTC is symmetric• If VTC is not symmetric we will find Wp/Wn
such that the VTC for an inverter is symmetric
![Page 3: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/3.jpg)
Allan Guan
What is VTC?• Voltage Transfer Curve• Plots output voltage vs. input voltage• Symmetry – when a line plotted through the origin and Vdd/2 intersects the VTC
at Vdd/2
![Page 4: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/4.jpg)
Allan Guan
Plotting the VTC• Open your inverter test bench from the 1st lab• Replace the pulse input with a DC source• Use the net label to label “in” and “out” of the inverter
![Page 5: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/5.jpg)
Allan Guan
Simulation Settings• Select DC sweep analysis• Set the source name to the name of your inverter’s input source
(IMPORTANT: add a ‘v’ in front of the name!)• Click OK, do NOT simulate
![Page 6: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/6.jpg)
Allan Guan
T-Spice• Click the “Open in T-Spice” button (T-icon to the right of the green play button)• Add the following lines of code• Hit the green play button
That vertical line is just the cursor, ignore that
![Page 7: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/7.jpg)
Allan Guan
The VTC is not symmetric
![Page 8: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/8.jpg)
Allan Guan
Obtaining a Symmetric VTC
• Keeping the length and width of the NMOS fixed we can vary the width of the PMOS to obtain a symmetric curve
• To do so, we will perform a DC sweep like before but with the addition of the parametric sweep
![Page 9: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/9.jpg)
Allan Guan
Setting up the Parametric Sweep
![Page 10: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/10.jpg)
Allan Guan
Defining the pMOS width as a parameter
• In the T-Spice code, write .param width=3u• In the pMOS properties, change W=3u to
W=‘width’• Now, the pMOS width is defined by parameter
‘width’
![Page 11: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/11.jpg)
Allan Guan
Your T-Spice code should look like this
![Page 12: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/12.jpg)
Allan Guan
Parametric Sweep Waveform
![Page 13: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/13.jpg)
Allan Guan
Designing with Symmetric VTC
• Click the trace to determine the width required for the symmetric VTC
• Record the width of the pMOS corresponding to the symmetric operating point (you should get 3.2u)
• Replace the inverter input with the original Pulse source
• Go back to simulation settings and uncheck the DC and parameter sweep and select Transient Analysis
• Open up the T-Spice command window and substitute this width for the pMOS and simulate
![Page 14: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/14.jpg)
Allan Guan
Rise/Fall Times @ Symmetric Operation
• In the W-Edit window, go to the waveform calculator
• Click “Measures…” and select “rise time”• Type in a trace name and press “Measure”• With the same trace, measure the “fall time”• Since we changed the pMOS width to obtain a
symmetric VTC, the rise and fall times should be the same
![Page 15: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/15.jpg)
Allan Guan
Power Consumption
• Now, we will use Tanner Tools to estimate the power consumption of a design
• We will also identify the sources of that consumption
![Page 16: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/16.jpg)
Allan Guan
Power Consumption
• Simulate the circuit over 2 periods with fine resolution (2ns)
• Show the waveforms for:– The input and output voltages– The power provided by the power supply– The currents drawn from the power supply and
the capacitor
![Page 17: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/17.jpg)
Allan Guan
Plotting Power and Current from the Transient Analysis
Get this capacitor from the Devices library
![Page 18: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/18.jpg)
Allan Guan
Power Consumption @10 pF load and 10ns rise time
![Page 19: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/19.jpg)
Allan Guan
Power Consumption @1 pF load and 10ns rise time
![Page 20: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/20.jpg)
Allan Guan
Power Consumption @1 pF load and 1ns rise time
![Page 21: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/21.jpg)
Allan Guan
Analysis
• Report numerical values of your results in tabular form.
• Can we vary the width of NMOS instead of PMOS in order to obtain symmetric VTC? If yes, should we increase or decrease it’s value keeping PMOS width fixed?
• On the VTC of the inverter, show the triode, saturation, and cut-off region. Which region is used for digital design and which one is used for analog design?
![Page 22: ECE 3130 – Digital Electronics and Design](https://reader036.fdocuments.net/reader036/viewer/2022062520/5681634c550346895dd3e329/html5/thumbnails/22.jpg)
Allan Guan
Analysis (Continued)
• Do you obtain different values of power consumed on varying the load and rise/fall time of the pulse? Compare and analyze your results.