Lab IV Lecture 1
Course Overview
Introduce Step 1
Course Web Page:
http://www.ece.drexel.edu/courses/ECE-L304
Course Goals
• Provide a practical experience in circuit
prototyping
• Integrate analog and digital circuit
design concepts
• Increase OrCAD skills
• Incorporate system-level and
scheduling considerations
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What Do We Expect of You?
• Attendance in lab lecture
• Attendance in lab hours
• You can work in a group of 2 and turn in one
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report
You will attend the lab section listed on your
schedule
• Work outside of lab hours
• This course is usually not finished in the allotted
lab time
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What Should You Expect?
• The materials and documentation
needed to perform the project
• Grade feedback on a timely basis
• Answers to your questions
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Grading Policy
• The deliverables for each step of the project
will receive a numerical grade. The grades for
steps which involve circuit design and
construction will have several parts, including
design, functionality, and quality of
construction.
• Multi-week labs will receive greater weight
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Grading Policy
• Pre-labs must be turned in with lab
reports.
• Deliverables are due no later than one
week after your scheduled lab meeting.
Reports which are late will lose 10% per
week until four week have gone by, at
which time the report will not be
accepted.
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Grading Policy
• Grading
• 10% quizzes (2)
• 90% labs (7 reports)
• Standard Grade Distribution
• ≥ 90% A
• 80 - 90 B
• Etc.
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The Overall Idea
• Design, build, debug and verify a digital
recording circuit, or data acquisition
system
• Accept analog information
• Convert to digital form
• Save to RAM
• Convert back to analog form
• Output across a load
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The Overall Idea
Data Bus
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ADC
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RAM
DAC
Control
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The Overall Idea
• Ideally we would like to be able to
record an audio (voice) message and
then play it back.
• We will see that there are real-world
limitations that will limit our success,
and some compromises will be needed.
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Step by Step
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Step 1 Review of ADC and DAC - simulation
Step 2 Build the ADC circuit - hardware
Step 3 Build the DAC circuit - hardware
Step 4 Introduce static RAM - simulation
Step 5 Build the on-board clock - hardware
Step 6 Introduce control logic - hardware
Step 7 Final changes - hardware
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Step 1- Review of DAC/ADC
• A simulation-based exercise
• Observe how analog signals are converted
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to digital signals
Observe how digital signals are converted
to analog signals
• The circuits observed are much simpler
than those in the hardware you will use,
but the concepts are similar
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Step 1 Prelab
• Read “Memory devices, timing models, and
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hierarchical blocks”, A. Motley, MicroSim
Corporation, April 1997 through the “The
Supporting Logic” section.
Review ADC, DAC experiments from ECEL
303 Lab III.
Find a box to safely carry around your circuit
(6” x 8” x 3” min).
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Step 1 Tasks
• Perform simulation
• Follow instructions on web site
• Lab Instructions:Step 1
• Complete “Workbook”
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Step 1 Method
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Think
Discuss
Draw
Simulate
Compare
Redraw if needed, but don’t erase
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Digital to Analog Conversion
• Digital signals have discrete levels
• MSB - highest weight
• LSB - lowest weight
• We must convert each N-bit binary
value to a unique analog voltage
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Discrete DAC
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Discrete DAC
4-bit counter
(not part of DAC)
TTL voltage
levels
Summing Amplifier
The values of the resistors in the input network of the summing amplifier
determines the “weights” of the digital bits.
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Analog to Digital Conversion
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ADC - Input Side
Schmidt
Trigger
Analog
Input
Voltage
Comparator
“DAC” signal from
R-2R Network
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ADC- Internal Voltage Generation
Binary Counter
R-2R
Network
D-Flip Flop
ADC Types
• The ADC chip we will use (ADC0804) is
based on a successive approximation (SA)
algorithm
• The SA Register and Latch (see the functional
diagram on the datasheet, p. 6-6) works like the
74161 counter in our simulation. The Ladder and
Decoder contains the R-2R network.
• The SA converter type is one of the most
commonly used
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Resolutions of ADC Types
Successive Approximation
Dual Slope
Sigma-Delta
Flash
Pipeline
0
5
10
15
20
25
Bits
Source: Aspects of data acquisition system design, P. Miller, TI Analog
Applications, Analog and Mixed-Signal Products, August 1999.
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Speeds of ADC Types
Successive Approximation
Dual Slope
Sigma-Delta
Flash
Pipeline
1
100
10000 1E+06 1E+08 1E+10
Samples per Second
Source: Aspects of data acquisition system design, P. Miller, TI Analog
Applications, Analog and Mixed-Signal Products, August 1999.
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Step 1 Deliverables
• A completed Chapter 11 workbook
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Discrete DAC summing ckt schematic
Discrete DAC summing ckt simulation
Integrated Ckt ADC schematics
Integrated Ckt ADC simulation
Answer Questions
Discrete Analog-to-Digital for extra credit
(10%)
• Due 1 week after lab date, in 7-205
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