Lec. 1:
Introduction to Data Convertors
Lecturer: Hooman Farkhani
Department of Electrical Engineering
Islamic Azad University of Najafabad
Feb. 2016.
Email: [email protected]
In The Name of Almighty
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Assignments
Homework: (15%)
Midterm Project: (25%)
Transistor level design and simulation of a data converter sub-
block (no layout)
Prepare a project report in the format and style of an IEEE jour
nal paper
Final Exam (60%)
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Tools and Technology
Primary tools
HSPICE 2011 or later
Cadence Virtuoso Schematic Editor with 0.18-μm model embe
dded
You can use your own tools/setups “at own risk“
Getting started
Read tutorials and setup info provided in HSPICE help
Technology
0.18-μm TSMC CMOS model
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Reference Books
M. Pelgrom, Analog-to-Digital Conversion, Springer, 2010.
Gustavsson, Wikner, Tan, CMOS Data Converters for Commu
nications, Kluwer, 2000.
A. Rodriguez-Vazquez, F. Medeiro, and E. Janssens, CMOS T
elecom Data Converters, Kluwer Academic Publishers, 2003.
W. Kester, The Data Conversion Handbook, Newnes, 2005.
B. Razavi, Data Conversion System Design, IEEE Press, 1995.
R. Schreier, G. Temes, Understanding Delta-Sigma Data Conv
erters, Wiley-IEEE Press, 2004.
R. v. d. Plassche, CMOS Integrated Analog-to-Digital and Dig
ital-to-Analog Converters, 2nd ed., Kluwer, 2003.
J. G. Proakis, and D. G. Manolakis, Digital Signal Processing,
Prentice Hall, 1995.
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An Analog Word
Everything in the physical world is an analog signal
i.e.: They are continuos and can take an inifinity of values
Sound, light, temperature, gravitational force
Need to convert into electrical signals
Transducers: converts one type of energy to another
Electro-mechanical, Photonic, Electrical, …
Examples
Microphone/speaker
Thermocouples
Accelerometers
x(t)
t
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An Analog Word
Transducers
Allow us to convert physical phenomena to a voltage potential in a well-
defined way.
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Data Converters: مبدل های داده - Analog to Digital Converter (ADC)
- Digital to Analog Converter (DAC)
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Data Converter Applications (1)
Consumer Electronics
- Audio, TV, Video
- Digital Cameras
- Automotive control
- Appliances
- Toys
- Sensors/instrumentation
Communications
- Mobile phones
- Personal Data Assistants
- Wireless Transceivers/ Wireline Communication
- Routers, Modems
- ……….
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Example (1)
A typical cell phone contains:
- 4 Rx ADCs
- 4 Tx DACs
- 3 Auxiliary ADCs
- 8 Auxiliary DACs
A total of 19 data converters!
Audio, Tx/Rx power control, Battery
charge control, display
Dual Standard. I/Q
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Basics: Analog-to-Digital Conversion
Conversion Process:
- 3 steps:
Sampling
Quantification
Coding
These operations are all performed in a same element:
The A to D Converter
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1. Sampling in Time:
• Digital system works with discrete states
• The signal is only defined at determined times
• The sampling times are proportional to the sampling period (Ts)
• Question 1: How fast can we sample the analog signal? (Sampling Rate) - Do a research on Nyquist sampling-rate ADCs.
xs(t=k*Ts) x(t)
Ts
x(t)
Ts
xs(t)
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2. Quantification
The signal can only take determined values
Belonging to a range of conversion (ΔVr)
• Based on number of bit combinations that the converter can output
• Number of possible states:
N=2n where n is number of bits
• Resolution: Q= ΔVr/N
t Ts
ΔVr Q
xq(t)
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2. Quantification (Cont.)
Example: Assume that Analog signal varies from 0 to 1.8V. We
want to digitize the input by 3 digits. Thus we have resolution=Q
=1.8/2^3 =225mV
For 6-bit ADC: Q=1.8/2^6=28mV.
For 8-bit ADC: Q=1.8/2^8=3mV.
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3. Coding
• Assigning a unique digital word to each sample
• Matching the digital word to the input signal
Analog Input
Voltage
Digital Output
Code
Step Width
(1 VLSB)
00
0
00
1
01
0
01
1
10
0
10
1
11
0
11
1
Vj
Vj+1
T[n]
T[1] T[2] T[3] T[4] T[5] T[6]
A
001
010
100100
100 100
Discretization Digitalization
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ADCs for different applications:
Medium Resolution; High-Speed ADCs (Gigabit Ethernet, Fas
t Ethernet)
6-7 bit 250Msps, 7-8 bit 125Msps
High Resolution; Medium-Speed ADCs (xDSL)
13-16 bit 35Msps; Low Power (VDSL)
Medium-to-High Resolution; Medium-to-High BW ADCs (zero-IF Receivers: 802.11, WiMAX)
10-12 bit 80Msps
Large DR; Highly Linear; Medium-to-High BW ADCs (IF Sampling, Multi-Standard: Software Radio Architectures)
12-16 bit 40-100Msps; SFDR > 90dB
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ADCs for different applications (cont.):
High Resolution Audio/Voice BW ADCs (CD/DVD Quality)
- 24 bit 192Ksps; Low Noise, Large DR
Medium-to-High Resolution; Medium-to-High BW ADCs (Im
aging & Video Processing: Imaging Devices, HDTV)
- 8-12 bit 40Msps, Low Power for Portables
Question(2):
For some especial applications, find the required resolution and
sampling rates of ADCs.
Question(3):
Do a brief research on history of ADCs/ DACs from 1950 till
now.
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ADC Landscape in 2004
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ADC Landscape in 2012
ADCs have become substantially “greener” over the years
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ADC landscape 2015
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Figure-of-Merit (FOM) versus frequency of operation
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Reference Books
M. Pelgrom, Analog-to-Digital Conversion, Springer, 2010.
Gustavsson, Wikner, Tan, CMOS Data Converters for Commu
nications, Kluwer, 2000.
A. Rodriguez-Vazquez, F. Medeiro and E. Janssens, CMOS T
elecom Data Converters, Kluwer Academic Publishers, 2003.
B. Razavi, Data Conversion system design, IEEE pres, 1995.
R. V. d. Plassche, CMOS Integrated Analog-to-Digital and Di
gital-to-Analog Converters, 2nd ed., Kluwer, 2003.
W. Kester, The Data Conversion Handbook, Newnes, 2005.
J. G. Proakis and D. G. Manolakis, Digital Signal Processing,
Prentice hall, 1995.
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References
Professor Boris Murmann Course slides 2013,
Stanford University- EE315B course
Dr. Reza Lotfi, ADC course slides 2008.
