Lec. 1: Introduction to Data Convertors

Lec. 1:

Introduction to Data Convertors

Lecturer: Hooman Farkhani

Department of Electrical Engineering Islamic Azad University of Najafabad Feb. 2016.

In The Name of Almighty

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%)

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

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.

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

An Analog Word

 Transducers

 Allow us to convert physical phenomena to a voltage potential in a well- defined way.

Data Converters: هداد یاه لدبم - Analog to Digital Converter (ADC)

- Digital to Analog Converter (DAC)

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

- ……….

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

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

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 (T_s)

• Question 1: How fast can we sample the analog signal?

x_s(t=k*T_s) x(t)

T_s

x(t)

T_s x_s(t)

2. Quantification

The signal can only take determined values Belonging to a range of conversion (ΔV_r)

• 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= ΔV_r/N

T_s t Q ΔVr

x_q(t)

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.

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)

000 001 010 011 100 101 110 111

V_j V_j+1

T[n]

T[1] T[2] T[3] T[4] T[5] T[6]

A

001

010

100 100 100 100

Discretization Digitalization

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,

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.

ADC Landscape in 2004

ADC Landscape in 2012

ADC landscape 2015

Figure-of-Merit (FOM) versus frequency of operation

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, 2^nd ed., Kluwer, 2003.

 W. Kester, The Data Conversion Handbook, Newnes, 2005.

 J. G. Proakis and D. G. Manolakis, Digital Signal Processing, Prentice hall, 1995.

References

 Professor Boris Murmann Course slides 2013, Stanford University- EE315B course

 Dr. Reza Lotfi, ADC course slides 2008.