very low power successive approximation a/d converter for instrumentation applications

146 Pages·2009·5.17 MB·English

UNIVERSITÀ DEGLI STUDI DI PAVIA

DIPARTIMENTO DI ELETTRONICA

DOTTORATO DI RICERCA
IN MICROELETTRONICA
XXII CICLO

V
ERY LOW POWER
S A
UCCESSIVE PPROXIMATION
A/D C
ONVERTER
I A
FOR NSTRUMENTATION PPLICATIONS

Relatore:
Chiar.mo Prof. Franco Maloberti

Coordinatore del Corso di Dottorato:
Chiar.mo Prof. Rinaldo Castello

Tesi di Dottorato
di Andrea Agnes

ANNO ACCADEMICO 2008 – 2009

TO MARTA

Contents I

Contents

Introduction .......................................................................... 1
- Motivations ................................................................................................................ 2
- Research goals ........................................................................................................... 5
- Thesis Organization ................................................................................................... 5
Ideal ADC ............................................................................. 7
- Basic A/D Conversion Concepts ............................................................................... 8
- Specifications........................................................................................................... 10
- Operation Issues ...................................................................................................... 32
Principle of Operation of SAR A/D Converter ................... 37
- Principle of S.A. Algorithm ..................................................................................... 38
- Architecture ............................................................................................................. 45
- State of the Art ......................................................................................................... 55
Design of each basic building block ................................... 59
- Principle of Design .................................................................................................. 60
- Building Blocks Design ........................................................................................... 62
- Prototype Implementation Details ........................................................................... 80
Experimental Results .......................................................... 87
- Measures .................................................................................................................. 88
- Setup ........................................................................................................................ 89
- Results ..................................................................................................................... 90
II Very low power Successive Approximation A/D Converter for Instrumentation Applications

Conclusions ........................................................................ 95
- Conclusions ............................................................................................................. 96
- Research products .................................................................................................... 97
- Acknowledgements ................................................................................................. 97
Other activities .................................................................... 99
- Chopper OpAmp.................................................................................................... 100
- Time Interleaved SAR ........................................................................................... 110
- Incremental Sigma-Delta ....................................................................................... 120
- Conclusions ........................................................................................................... 133
Ringraziamenti .................................................................. 137
Contents III
IV Very low power Successive Approximation A/D Converter for Instrumentation Applications
Ch. 1 - Introduction 1

1

Introduction

•
Motivations
•
Research Goals
•
Thesis Organization
2 Very low power Successive Approximation A/D Converter for Instrumentation Applications

1.1 Motivations

I
n recent years the medical evolution allows us to get always better results, for example now
is possible to understand the causes of some illness and prevent them with particular attention, or
also when the illness is already done, it is possible to eliminate every trace and consequence of its
passage. Unfortunately this ideal world has not been reached yet. Sometime there are illnesses
which are not possible to take care of definitively, and require a continuous control for how much
and what medicines are necessary to not worsen the
conditions of the patient. To solve completely the
effects of this typology of illnesses, unfortunately, is
not possible using electronic science but it can help
this type of patient for getting better their style of
life. For example, people with diabetes have to
constantly hold under observation own glucose level
in blood and, consequently, to inject the required
dosing of insulin to avoid possible dangerous crises.
There are almost 250 million people affected by
The Gluco-test used for measuring glucose by
diabetes worldwide and the number is expected to
introducing the drop of blood token from capillary
in the finger.
grow over the next decade due to population
Source: www.118pescara.it
growth, ageing and life style. Without proper
treatment, diabetes can lead to cardiovascular disease, kidney failure, blindness, nerve damage, and
ultimately death. Diabetes is a leading cause of death in most developed countries. These people
usually control their glucose level by stinging their own finger and withdrawing a drop of blood.
This drop will be insert in a particular machine which can analyze the blood and returns the glucose
level found. When the person knows the value then can assume the right dosage of insulin by
injection with syringe. Electronic science, in this
environment, had designed test machine for analyzing
blood always smaller and the required quantity of
blood to ensure a correct value is always less. These
last technological steps allow to keep under control the
Syringe typically adopted by diabetic people for
injecting the correct insulin dosage, the shape is critical parameter everywhere, using a little machine
studied for children use.
Source: www.bioblog.it with dimension comparable with a normal mobile
phone.