Lec. 1:

Introduction to Data Convertors

Lecturer: Hooman Farkhani

Department of Electrical Engineering

Islamic Azad University of Najafabad

Feb. 2016.

Email: H_farkhani@yahoo.com

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%)

3

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.