Converter Simulation - Beyond the Evaluation Board

The World Leader in High Performance Signal Processing Solutions

Converter Simulation – Beyond

the Evaluation Board

Analog Devices’ Approach to Behavioral Modeling

By: Tom MacLeod

Outline

Modeling OverviewWho am I?

What is Converter Simulation?

Why Model at All?

How Does One Model Behavior?

How Does One Model Converter Behavior?

Modeling Converter Behavior

Can behavioral modeling be any good?

What can converter modeling do for me?

Does Analog Devices currently have a converter modeling tool?

What is the Future for Behavioral Modeling?

Review

Q&A

2

Who am I?

My name is Tom MacLeod

Applications/Software Engineer for the Converter System Applications group

Developer of ADIsimADC™

Developer of Tools/Scripts for the lab

Traditional Applications for High Speed ADCs

Been with ADI for 7.578 years

Graduated from North Carolina State University


It is a “top down” or “black box” approach to modeling a converter (inherently a mixed signal device)

It models the “what” as opposed to the “how”

Models the transfer function rather than multi-stage pipeline

Models harmonic distortion rather than transistor imbalance within a current mirror of an input buffer

It implements a unique strategy, modeling characteristics of interest (proxies) without needing to know the circuit level implementation

What is Converter Simulation? (cont.)

The concept of modeling converter proxies generalizes to a modeling philosophy known as “behavioral modeling”

Behavioral Modeling – the ability to model apparent behavior of a process or entity without simulating the complex internal subsystems which yield such behavior

Example: IBIS (Input Output Buffer Information Specification ) Models IBIS is a method of providing information about the input/output buffers of

an integrated circuit to the outside world. It is an EIA (Electronic Industries Alliance) standard. The idea of IBIS is to provide the behavioral aspects of a circuit without providing the actual circuit information to the user. – Wikipedia

Models: Current vs. Voltage Voltage vs. Time

What is Converter Simulation? (cont.)

What behavioral modeling is not

Not SPICE (Simulation Program with Integrated Circuit Emphasis)

General-purpose analog electric circuit simulator

Not a database

Not Evaluation Software

Why Model at All?

Simulation is becoming heavily used in system design and initial characterization to reduce risk and cost

Modeling communicates information about new products more quickly and comprehensively than traditional means of product introduction

Modeling communicates information about our current portfolio more efficiently and intuitively to the “young kids with their iPods and videogames”

Why Model at All? (cont.)

Benefits of Behavioral Modeling

Reduces the technical complexity of the modeling tool

Decreases simulation time

Increases productivity and user satisfaction

Abstracts implementation and consequently intellectual property

Leverages reuse of modeling tool for similar products

Can parameterize proxies thus providing a framework to support similar products

Simplifies model creation process

Important when creating and maintaining hundreds of products


Answer: Math Models!

Example – Gaussian Distribution

Example – Population Growth


A model should faithfully reproduce converter proxies (both static and dynamic) such as:

Offset

Gain

Quantization

Sample Rate Dependencies

Input Bandwidth

Jitter Sensitivity

Latency

AC and DC Linearity

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Modeling Converter Behavior (cont.)

It should be flexible enough to support different architectures

Pipeline

Delta-Sigma

SAR

Support many “bolt-on” features

Numerically Controlled Oscillators

Digital Filters

Noise Shapers

Analog Filters

Low Noise Amplifiers

Variable Gain Amplifiers

Modeling Converter Behavior (cont.)

A model should be contained within a library so that it can be called from multiple applications

Dynamic Linked Library (DLL)


Model

Physical

Part = AD6645

Model

Can behavioral modeling be any good? (cont.)

AD9271(Octal LNA/VGA/AAF/ADC)

Model

Physical


Live datasheet

Find typical performance not explicitly listed on the static datasheet

Part = AD9229, Ain = 49.3 MHz

SNR = 68 dB, 2nd = -82.8, 3rd = -80.3

What can converter modeling do for me? (cont.)

Didactic

Consider impact on performance from jitter (AN-501)

AD9246, Ain = 2.3 MHz, fs = 125 MSPS

Calculate “composite DNL”

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AD9246, Ain = 201.3 MHz, fs = 125 MSPS

13 fsec difference

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Didactic

Consider effects of adding band limited dither

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Without Dither With Dither


Product selection

Find the product that meets your requirements under your conditions

Welcome to the online ADIsimADC Design Toolhttp://www.analog.com/adisimadc

Click here

http://www.analog.com/adisimadc


Input your

requirements

(SNR > 78 dB

SFDR <= -85 dBc)

Click here

Input your

conditions


Models that met

my requirements


It worked!

SNR = 78 dB

SFDR = -93 dBc

What’s 100k

volume pricing?


Product Evaluation

A subset of products (those ending in .PMF) support a register map interface

Example – AD6657

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Tuning word changed from 28 to 0

Same as real device

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System Level Simulation

Simulate the effects a particular ADC will have on your system

LTE Uplink (5 MHz) waveform

AD6655 (14-bit IF receiver)

SNR = 65.7 dB

Does Analog Devices currently have a

converter modeling tool?

Yes - ADIsimADC

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Where can I buy ADIsimADC?

You can’t buy it! It’s free!

Visit: http://www.analog.com/adisimadc

As part of ADI’s “whole product initiative”

There is no cost to use this tool; use it in whatever environment you prefer

+ =

http://www.analog.com/adisimadc

Where can I buy ADIsimADC? (cont.)

We package it with VisualAnalog (also free)

Just install VisualAnalog, run it,

browse for your favorite ADC,

select it and start modeling!

Also available as an

online design tool

What products are currently supported?

AD6645_105 AD9214_105_1V AD9218_80_1V AD9230_210 AD9238_20 AD9246_105 AD9255_125 AD9268_80 AD9445_105_3p2V AD9600 AD9629_40 AD80141 AD9230 AD9252 AD9287 AD9609

AD6645_80 AD9214_65_2V AD9219_40 AD9230_250 AD9238_40 AD9246_125 AD9255_80 AD9271 AD9445_125_2V AD9601 AD9629_65 AD9204 AD9231 AD9254 AD9289 AD9626

AD6655 AD9214_80_1V AD9219_65 AD9231_20 AD9238_65 AD9248_20 AD9258_105 AD9272 AD9445_125_3p2V AD9609_20 AD9629_80 AD9211 AD9233 AD9255 AD9430 AD9627-11

AD6657 AD9215_105 AD9222_40 AD9231_40 AD9239_170 AD9248_40 AD9258_125 AD9273 AD9446_100_2V AD9609_40 AD9640 AD9214 AD9236 AD9258 AD9433 AD9627

AD80141 AD9215_65 AD9222_50 AD9231_65 AD9239_210 AD9248_65 AD9258_80 AD9287 AD9446_100_3p2V AD9609_65 AD9644_80 AD9215 AD9237 AD9259 AD9444 AD9629

AD9204_20 AD9215_80 AD9222_65 AD9231_80 AD9239_250 AD9251_20 AD9259 AD9289 AD9446_80_2V AD9609_80 AD9649_20 AD9216 AD9238 AD9262 AD9445 AD9640

AD9204_40 AD9216_105 AD9226_2V AD9233_105 AD9244_40 AD9251_40 AD9262 AD9430_170_LVDS AD9446_80_3p2V AD9626_170 AD9649_40 AD9218 AD9239 AD9265 AD9446 AD9644

AD9204_65 AD9216_65 AD9228_40 AD9233_125 AD9244_65 AD9251_65 AD9265_105 AD9430_210_LVDS AD9460_105_3p4V AD9626_210 AD9649_65 AD9219 AD9244 AD9268 AD9460 AD9649

AD9204_80 AD9216_80 AD9228_65 AD9236 AD9245_20 AD9251_80 AD9265_125 AD9433_105 AD9460_80_3p4V AD9626_250 AD9649_80 AD9222 AD9245 AD9269 AD9461

AD9211_200 AD9218_105_1V AD9229_50 AD9237_20 AD9245_40 AD9252 AD9265_80 AD9433_125 AD9461_125_3p4V AD9627-11 AD6645 AD9226 AD9246 AD9271 AD9480

AD9211_250 AD9218_40_1V AD9229_65 AD9237_40 AD9245_65 AD9254 AD9268_105 AD9444 AD9461_130_3p4V AD9627 AD6655 AD9228 AD9248 AD9272 AD9600

AD9211_300 AD9218_65_2V AD9230_170 AD9237_65 AD9245_80 AD9255_105 AD9268_125 AD9445_105_2V AD9480 AD9629_20 AD6657 AD9229 AD9251 AD9273 AD9601

All high speed (>20 MSPS) ADCs for the last 5 years. 188 models so far…

What is the Future for ADIsimADC?

Support for high-precision ADCs <20 MSPS

16-bit to 24-bit delta sigmas and PULSARs

Depends on proxies we identify are important

Support for more accurate models

Better integration with SPI control software

User defined phase noise profiles

Arbitrarily oversampled inputs

Statistical distribution of products (Monte Carlo)

Temperature sensitivities

Open to suggestions!

What is the Future of Behavioral Modeling?

Support for precision ADCs

Support for DACs

Support for clocks

Support for amplifiers

Support for modulators/demodulators

Need feedback!

Outline



Why Model at All?








Review

Q&A

32

Review

Behavioral modeling has been shown to be a viable and effective technology

Purposes

Live datasheet

Didactic

Product selection

Product evaluation

System level simulation

Analog Devices freely offers ADIsimADC, a converter behavioral modeling tool as part of its “whole product” initiative

We want this tool to be part of a dialog between you and us

Give us feedback

Provide suggestions

Try and break it

Analog Devices is committed to maturing this technology

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Next webcast

RF Detectors February 16th at Noon (ET)

Challenges in Embedded Design for real-time systems

March 16th at Noon (ET)

34

www.analog.com/webcast

Fundamentals Webcasts 2011

January Introduction and Fundamentals of Sensors

February The Op Amp

March Beyond the Op Amp

April Converters, Part 1, Understanding Sampled Data Systems

May Converters, Part 2, Digital-to-Analog Converters

June Converters, Part 3, Analog-to-Digital Converters

July Powering your circuit

August RF: Making your circuit mobile

September Fundamentals of DSP/Embedded System design

October Challenges in Industrial Design

November Tips and Tricks for laying out your PC board

December Final Exam, Ask Analog Devices

www.analog.com/webcast

Outline



Why Model at All?








Review

Q&A

36

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Converter Simulation - Beyond the Evaluation Board