Transcript

BITS Pilani Pilani Campus BITS Pilani Pilani Campus

ANU GUPTA EEE

Analog I C Design MEL G632

BITS Pilani Pilani Campus BITS Pilani Pilani Campus Anu Gupta

AICD Lecture 1

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Introduction

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Instructor-in-charge : ANU GUPTA Email (I/C): anug@pilani.bits-pilani.ac.in

Analog I C Design MEL G632

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The objective of this course is to teach

analog integrated circuit design using

today’s technologies and in particular,

CMOS technology.

Objective

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The (electronic) world is going Digital,

why Analog?

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While many applications have replaced much analog circuitry with their digital counterparts, the need for analog circuit design is actually growing.

REASON 1------- Consumer-focused electronics have become the driving force of

industry, But , consumer electronics has become all-digital, networked,

sophisticated, and almost independent of time, place, physical embodiment, and content.

Users expect their tailored audio and video content when, where, and how they want it, to their own schedule and convenience.

NEED

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Ans.---As the digital demands have increased, they have increased the demands on analog as well, which is good for R&D and production investment. Ironically, new requirements for features in digital cell phones are dictating the needs for new analog functions.

And in turn, the increased analog capability has enabled more the

desired digital functionality and performance, as well. So we have one of the few cases where a positive feedback loop

is for good Example---Electronic application in demand

CELL PHONE

Reason 1--Consumer-focused electronics

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The key components of a basic handset are the radio, the power management, and the analog and digital baseband processing.

Basic Digital Handset

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Interesting fact: There's more analog in a digital

handset than in an analog model

Analog in digital handset.

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In a digital handset, --convert the voice signal to a digital stream (with an "analog" ADC). ---But before conversion, need to filter it (using an analog filter). --What comes out to your ear must be converted from digital to analog.(DAC) --And there's an analog filter there to clean up that signal. Getting the signal up onto the RF carrier, ---power amplifier (PA), --analog circuitry is needed to control the PA to ramp it up and down, and to

control the power,

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Putting the signal up on the air waves generally requires turning bits into a modulated carrier, which requires DACs and some filters (more analog parts).

On the receive side, what comes down from the RF

carrier is a modulated signal that needs ADCs to decompose the signal into quadrature components.

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The battery and power management CIRCUIT

that's needed to handle all the new digital

"stuff“ that's being packed into the newer

models, like things to manage a color display,

and the backlighting for it, high-performance

audio, and so on.

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Modern Handset

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• Higher resolution camera---analog image processing required to interface a multi-

megapixel camera sensor to the digital processor,

• Music-player phones with iPod-like capabilities----high-quality playback digital-to-

analog converters (DACs) and headphone driver amplifiers for audio playback.

• TV reception is a new feature emerging in cell phones----keeping the display

brightly lit to watch a video clip without consuming too much power requires power

management. power-management and battery-monitoring/charging functions needed

to maximize battery life while powering all the new features.

• Emerging TV-related feature is the ability to play back recorded still photos and

short video clips from the phone to a TV set. This requires creating an analog video

signal from the digitally-stored photo or video clip.

• Games---improved graphics capability, user interfaces, and even sound effects.

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Also, as the clock speed of digital circuitry

approaches 1 GHz, analog effects in these digital

circuits are playing an important role in the circuit

behavior.

Reason2- High speed

Which Analog circuits are important?

• If not for the multitude of analog and mixed-signal components that vendors have

developed in the past decades, the digital media river would slow to a trickle. It takes

countless A/D and D/A converters—audio, video, RF—to make it possible.

• It also takes basic small-signal amplifiers, audio through RF power amplifiers,

• disk-drive read/write circuitry,

• motor controls, line drivers and receivers, transmitters,

• power-supply components,

• touch-screen interfaces, display drivers,

• thermal sensors and fan controls,

and much more, to make the digital world possible.

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Analog IC Design

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The aim of this course is

to help students conceive, develop, debug

analog integrated circuits by presenting a

concise treatment of the wide array of

knowledge required by an analog IC

designer.

Aim while teaching

Approach to be followed a. Develop a firm background on technology and

modeling

b. Present analog integrated circuits in a hierarchical, bottom-up manner

c. Emphasize understanding and concept over analytical methods (simple models)

d. Illustrate the correct usage of the simulator in design

e. Develop design procedures that permit the novice to design complex analog circuits

(these procedures will be modified with experience)

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Presenting the fundamentals required to build high-

performance analog systems, -----will help to take the

mystery out of analog design.

In all cases , emphasis on the most important and

fundamental principles as they pertain to state-of-the-art

analog design.

Emphasis

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Course Handout

Component Duration Weightage

Date, & Time Remarks

Mid-semester Test 90 min 25 OB

Analog design project / take home weekly lab-assignments

continuous 40 Spread throughout the semester

OB

Comprehensive 3 hrs. 35 CB

100

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• Basic knowledge about single stage amplifiers

• Modelling

• AC., DC. Analysis techniques

• Frequency response analysis

• Negative feedback

Required background knowledge

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• Analog Integrated Circuit Design

• Technology Impact on Analog IC Design

• Analog Signal Processing functions

• Notation, Symbology and Terminology

• Summary

Introduction

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Geometry is an important part of the design Electrical Design →Physical Design →Test

Design Usually implemented in a mixed analog-digital

circuit Analog is 20% and digital 80% of the chip area Analog requires 80% of the design time Analog is designed at the circuit level Passes for success: 2-3 for analog, 1 for digital

Unique Features of Analog IC Design

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The Analog IC Design Flow

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Electrical Aspects-Topology, W/L values, and dc currents

Analog IC Design - Continued

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Physical Aspects-(Layout)

-Implementation of the physical design including:

- Transistors and passive components

- Connections between the above

- Busses for power and clock distribution

- External connections

Testing Aspects

-Design and implementation for the experimental verification of the circuit after fabrication

Analog IC Design - Continued

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Comparison of Analog and Digital Circuits

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In general, analog circuits are more complex than digital

Requires an ability to grasp multiple concepts simultaneously

Must be able to make appropriate simplifications and assumptions

Requires a good grasp of both modeling and technology

Have a wide range of skills - breadth (analog only is rare)

Be able to learn from failure

Be able to use simulation correctly

Simulation “truths”:---(Usage of a simulator) x (Common sense) = Constant

Simulators are only as good as the models and the knowledge of those models by

the designer

Simulators are only good if you already know the answers

Skills Required for Analog IC Design

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Complexity as a Function of the Number of Transistors

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Technology Impact On Analog IC Design

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Moore’s law: The minimum feature size

tends to decrease by a approx. factor

of 1/ 2 every three years.

Semiconductor Industry Association roadmap for CMOS

Trends in CMOS Technology

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Technology Speed: Figure of Merit vs. Time:

Trends in IC Technology

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A steeper ramp for the IC design development is required for every new generation of technology

IC Design Development Time

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The good:

Smaller geometries, Smaller parasitics, Higher transconductance, Higher

bandwidths

The bad:

• Reduced voltages, Smaller channel resistances (lower gain),More

nonlinearity, Deviation from square-law behavior

The ugly:

• Increased substrate noise in mixed signal applications, Increased 1/f

noise below 0.25µm CMOS, Threshold voltages are not scaling with

power supply, Suitable models for analog design not available

Technology impact on IC Design

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Threshold voltages and power supply

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Frequency Performance based on Scaling

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Innovation in Analog IC Design

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Technology-Driven versus Application-Driven Innovation

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Application driven circuit innovation

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• Scramble to develop new tools

• Complexity is increasing with each new

scaling generation

• Need more trained and skilled circuit

designers

Results:

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Signal Bandwidths versus Application

Analog Signal Processing

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Signal Bandwidths versus Technology

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There are established fields of application:

• Digital-analog and analog-digital conversion

• Disk drive controllers-circuit which allows the CPU to communicate with a hard

disk, floppy disk or other kind of disk drive

• Modems , filters---A modem is a device that modulates an analogue carrier

signal to encode digital information, and also demodulates such a carrier signal

to decode the transmitted information. The goal is to produce a signal that can

be transmitted easily and decoded to reproduce the original digital data

Analog IC Design has Reached Maturity

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• Codecs---A codec is a device or program capable of

performing encoding and decoding on a digital data stream or

signal.

• Bandgap reference

• Analog phase locked loops

• DC-DC conversion

• Buffers

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Regarding analog circuits:

“If it can be done economically by digital,

don’t use analog.”

Existing philosophy

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Analog finds applications where speed, area, or power have advantages over a digital approach.

Consequently

Eggshell Analogy of Analog IC Design (Paul Gray)

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Key issues:

• Analog/Digital mix is application

dependent Not scaling driven

•Driven by system requirements for

programmability/adaptability/testability/desig

nability

Analog Signal Processing versus Digital Signal Processing in VLSI

Application Areas of Analog IC Design

• There are two major areas of analog IC design:

• • Restituitive - performance oriented (speed, accuracy, power, area)

Classical analog circuit and systems design

• Cognitive - function oriented (adaptable, massively parallel)

A newly growing area inspired by biological systems

Analog VLSI (An oxymoron):

• Combination of analog circuits and VLSI

philosophies

Many similarities between analog circuits and biological systems

• Scalability

• Nonlinearity

• Adaptability

Neuromorphic analog VLSI

• Use of biological systems to inspire circuit design such as smart sensors and imagers

Smart autonomous systems

• Self-guided vehicles (Mars lander)

• Industrial cleanup in a hazardous environment

Sensorimotor feedback

• Self contained systems with sensor input, motor output

What is the Future of Analog IC Design?

• • Technology will require more creative circuit solutions in

order to achieve desired performance

• • Analog circuits will continue to be a part of large VLSI

digital systems

• • Interference and noise will become even more serious as

the chip complexity increases

• • Packaging will be an important issue and offers some

interesting solutions

• • Analog circuits will always be at the cutting edge of

performance

• • Analog designer must also be both a circuit and systems designer and must know:

-Technology and modeling

-Analog circuit design

-VLSI digital design

-System application concepts

• • There will be no significantly new and different technologies - innovation will combine new applications with existing or improved technologies

• • Semicustom methodology will eventually evolve with

CAD tools that will allow:

- Design capture and reuse

- Quick extraction of model parameters from new

technology

- Test design

- Automated design and layout of simple analog circuits

NOTATION, SYMBOLOGY, AND TERMINOLOGY

Example:

MOS Transistor Symbols

Other Schematic Symbols

SUMMARY

• • Analog IC design combines a function or application with

IC technology for a successful solution.

• • Analog IC design consists of three major steps:

• 1.) Electrical design , Topology, W/L values, and dc currents

• 2.) Physical design (Layout)

• 3.) Test design (Testing)

• • Analog designers must be flexible and have a skill set that

allows one to simplify and understand a complex problem

• • Analog IC design is driven by improving technologies

rather than new technologies.

• • Analog IC design has reached maturity and is here to stay.

• • The appropriate philosophy is “If it can be done

economically by digital, don’t use analog”.

• • As a result of the above, analog finds applications where

speed, area, or power have advantages over a digital

approach.

• • Deep-submicron technologies will offer severe challenges

to the creativity of the analog designer.

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END

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