Download Digital Circuit Simulations

Digital Circuit
Simulations
Deborah Barnett, Tidehaven High School
Tidehaven ISD
Dr. Peng Li, Assistant Professor (faculty mentor)
Department of Electrical and Computer Engineering
Texas A & M University
Ping-Hsiu Lee, Reagan High School
Houston ISD
(research partner)
THE LAB
RESEARCH: THREE MAIN THEMES
• FIRST THEME: design automation of
electronic circuits and systems, also
commonly referred to as VLSI CAD
VLSI means Very Large Scale Integration
CAD means Computer Aided Design
……
• SECOND THEME: built-in self-test of
analog/mixed-signal ICs and tunable
circuit design,
IC means Integrated Circuit
• THIRD THEME: parallel methods for
large-scale computing problems
encountered in integrated circuit design
and other computing applications .
Current research topics
in the Department of Electrical and
Computer Engineering Lab:
• Parallel VLSI CAD algorithms
and their implementation on
multicore and distributed
platforms
……….and
• Tunable design/built-in-selftest/CAD for analog/mixedsignal ICs
……and
• CAD for multicore chip designs
and embedded memories
……and
• Analysis and design of IC
power/ground distribution &
clock networks
….and
• Massively parallel GPU (Global
Processing Unit) computing for VLSI
design and general
computing applications
…..and finally, the one we’re
involved in…..
• Statistical circuit design,
circuit simulation, interconnect
and timing
BACKGROUND on research
SPICE
•
•
•
•
•
Simulation
Program for
Integrated
Circuits
Emphasis
• SPICE is a powerful general
purpose analog circuit
simulator that is used to verify
circuit designs and to predict
the circuit behavior. This is of
particular importance for
integrated circuits.
• SPICE was originally
developed at the Electronics
Research Laboratory of the
University of California,
Berkeley (1975).
PSPICE
• PSpice is a SPICE analog circuit and
digital logic simulation software that runs
on personal computers. It was developed
by MicroSim and is used in electronic
design automation.
MORE BACKGROUND TO
KNOW FOR RESEARCH
• analog circuit, electronic circuit that
operates with currents and voltages that
vary continuously with time and have no
abrupt transitions between levels.
And More ….
• Digital circuits are electronic circuits that
take on only a finite number of states.
• Binary (two-state) digital circuits are the
most common.
ANALOG vs DIGITAL
• Generally speaking, the voltage of analog
circuits vary in a continuous manner while
when working with digital circuits, we are
interested in when the circuit is on or off.
In other words, we consider them as a
binary circuit.
THE BASIC DIGITAL CIRCUIT
The basic digital circuit for our research
design consists of a pull-down network
and a pull-up network.
The input and output of the circuit is
binary, 0 or 1.
(0 for off and 1 for on)
THE CIRCUIT
For the pull-down network (or nMOS) to be
active, the output must be 0. For the pullup network (or pMOS) to be active, the
output must be 1.
nMOS means negative Metal Oxide Semiconductor
pMOS means positive Metal Oxide Semiconductor
Designing a Circuit
We need to consider the duality rule for
circuit design.
The duality rule part 1 : If there is a nMOS
on the pull-down, then there will be a
pMOS on the pull-up and vice versa.
EXAMPLE of a circuit in action when the
input is 0
A
in
0
Y
out
1
Y=1
OFF
Y
The duality in this system is shown with the
pull-down to ground as nMOS and the pullup to VDD as pMOS
(drain)
ON
A=0
1
A
VDD
GND
(source)
EXAMPLE of a circuit in action when the
input is 1
A
Y
0
1
1
0
VDD
OFF
A=1
Y=0
ON
A
Y
GND
More on Duality
• Duality Rule part 2: transistors that
appear in series in the pull-down network
must appear in parallel in the pull-up
network and vice versa.
Duality Design
Parallel transistors
pMOS
Y
A
B
Series transistors
nMOS
RELEVANCE/
REAL WORLD APPLICATION
• Computers, calculators, cell phones….. all
depend on microchip design to work. We
continue to want our technology to work
faster and more efficiently. Design is the
first step in making it happen.
OVERVIEW OF OUR RESEARCH
PROJECT
OBJECTIVE
• Graphically (by hand) design and analyze
circuit functionality and performance.
MODELING
• Model basic CMOS transistor behavior
using simple switch models and more
sophisticated continuous models.
CMOS means Complementary Metal Oxide Semiconductor
DATA INTERPRETATION
• Verify graphical analysis (our circuit
design) and model behavior using the
simulation program PSPICE.
SUMMARY
The design of the microchip is essential to its use
in various technologies. To understand the
basic design of the integrated circuits, our
research will model simple CMOS transistor
behavior using simple switch models and other
continuous models. We use PSPICE simulation
to verify our hand (graphical) analysis of circuit
functionality and performance.
CLASSROOM PROJECT
This will be an integrated
curriculum project with
English 1, IPC and Algebra 1.
CLASSROOM PROJECT
The student will
• investigate the development of the microchip
and its uses in modern technology
• construct an electrical transistor and investigate
the physical design of the microchip
• design simple CMOS transistors
• use PSPICE to analyze their designs
REFERENCES
Lectures, Dr. Peng Li
Weste, N. H. E. and Harris, D. (2005) CMOS VSLI
Design: A circuits and Systems Perspective.
Boston, MA: Pearson, Addison Wesley.
www.seas.upenn.edu
ACKNOWLEDGEMENTS
•
•
•
•
Dr. Peng Li, faculty mentor
TAMU E3 participating faculty
National Science Foundation (NSF)
Ping-Hsiu Lee, partner