ECEN474: (Analog) VLSI Circuit Design Fall 2012
Lecture 1: Introduction
Sam Palermo Analog & Mixed-Signal Center Texas A&M University
Analog Circuit Sequence
326
Why is Analog Important?
[Silva]
Naturally occurring signals are analog Analog circuits are required to amplify and condition the signal for further processing Performance of analog circuits often determine whether the chip works or not Examples
Sensors and actuators (imagers, MEMS) RF transceivers Microprocessor circuits (PLL, high-speed I/O, thermal sensor)
3
Integrated Circuits
[Bohr ISSCC 2009]
4-core Microprocessor (45nm CMOS)
Mostly Digital Noteable analog blocks
PLL, I/O circuits, thermal sensor
[Sowlati ISSCC 2009]
Cellular Transceiver (0.13m CMOS)
Considerable analog & digital
[Pertijs ISSCC 2009]
Instrumentation Amplifier (0.5m CMOS)
Mostly Analog Some Digital Control Logic
4
The Power of CMOS Scaling
[Bohr ISSCC 2009]
Scaling transistor dimensions allows for improved performance, reduced power, and reduced cost/transistor Assuming you can afford to build the fab
32nm CMOS fab ~3-4 BILLION dollars
5
Course Topics
CMOS technology
Active and passive devices Layout techniques
MOS circuit building blocks
Single-stage amplifiers, current mirrors, differential pairs
Amplifiers and advanced circuit techiques
Course Goals
Learn analog CMOS design approaches
Specification Circuit Topology Circuit Simulation Layout Fabrication
Understand CMOS technology from a design perspective
Device modeling and layout techniques
Use circuit building blocks to construct moderately complex analog circuits
Multi-stage amplifiers, filters, simple data converters,
Administrative
Instructor:
Sam Palermo 315E WERC Bldg., 845-4114, spalermo@ece.tamu.edu Office hours: MW 3:00pm-4:30pm
Lectures: MWF 9:10am-10am, ETB 1037 Class web page
http://www.ece.tamu.edu/~spalermo/ecen474.html
Class Material
Textbook: Design of Analog CMOS Integrated Circuits, B. Razavi, McGraw-Hill, 2001. (Optional) References
Analog Integrated Circuit Design, D. Johns and K. Martin, John Wiley & Sons, 1997. Analysis and Design of Analog Integrated Circuits, P. Gray, R. Meyer, P. Hurst, and S. Lewis, John Wiley & Sons, 4th Edition, 2003. Technical Papers
Class notes
Posted on the web and will hand out hard copies in class
Grading
Exams (60%)
Three midterm exams (20% each)
Homework (10%)
Collaboration is allowed, but independent simulations and write-ups Need to setup CADENCE simulation environment No late homework will be graded
Laboratory (20%) Final Project (10%)
Groups of 1-2 students Report and PowerPoint presentation required
10
Preliminary Schedule
Dates may change with reasonable notice
11
Reading
Razavi Chapter 2 & 16
12
Analog IC Design Olympics (Extra Credit)
Analog IC Design Olympics Contest is on September 15
http://amsc.tamu.edu/olympics.htm Register by August 31 at noon
Open to all TAMU Grad Students Teams of 2 will compete in a circuit design contest Designs are judged by a distinguished industrial committee
Broadcom, NXP, Qualcomm, Silicon Labs, TSMC, TI, Stone Soup Labs
Extra Credit Opportunity for Grad Students
20 points added to a homework score Undergrads will have an extra credit opportunity later in the semester
13
CMOS Technology Overview
MOS Transistors Interconnect Diodes Resistors Capacitors Inductors Bipolar Transistors
14
CMOS Technology
[Razavi]
NMOS
PMOS
15
NMOS Transistor
Source Metal 1 CVD Oxide Drain Poly Gate n+ Gate Oxide p substrate Bulk
Gate
[Silva]
NMOS Symbols
n+
Cross Section
Source Bulk
Drain
Circuit Symbol
n+
Poly
n+
Top View
16
PMOS Transistor
Drain Metal 1 CVD Oxide Source Poly Gate p+ Gate Oxide n-well Bulk p substrate Bulk
Gate
[Silva]
PMOS Symbols
p+
Cross Section
Drain Bulk
Source
Circuit Symbol
n-well
n+
Poly
n+
Top View
17
Todays CMOS Transistors
[Bohr ISSCC 2009]
Todays transistors have advanced device structures Most advanced transistors are moving from poly-gates back to metal-gates
Allows for High-K gate dielectric and reduced gate leakage current
18
Interconnect (Wires)
[Bohr ISSCC 2009]
19
Diodes
[Silva] Anode Cathode Typical values: P+=1017-1019 acceptors /cm3 P=1015-1017 acceptors /cm3 A SiO2 P+ Diode N N+ Contact C N=1016-1018 donors/cm3 N+=1017-1019 donors/cm3 Metal 5x1022 electrons/cm3
Bulk (substrate) P-type
20
Resistors
Poly Resistor Nwell Resistor [Razavi]
Different resistor types have varying levels of accuracy and temperature and voltage sensitivities
21
Capacitors
Poly - Diffusion Poly - Poly Metal1 - Poly
[Razavi] Vertical Metal Sandwich
Lateral Metal-Oxide-Metal (MOM)
[Wang]
[Ho]
22
Inductors
[Silva/Park]
Inductors are generally too big for widespread use in analog IC design
Can fit thousands of transistors in a typical inductor area (100m x 100m)
Useful to extend amplifier bandwidth at zero power cost (but significant area cost)
23
Bipolar Transistors Vertical PNP
[Johns] Vertical PNP Bandgap Reference
Useful in a precise voltage reference circuit commonly implemented in ICs (Bandgap Reference)
24
Bipolar Transistors Latchup
[Razavi] Equivalent Circuit
Potential for parasitic BJTs (Vertical PNP and Lateral NPN) to form a positive feedback loop circuit If circuit is triggered, due to current injected into substrate, then a large current can be drawn through the circuit and cause damage Important to minimize substrate and well resistance with many contacts/guard rings
25
Next Time
MOS Transistor Modeling
DC I-V Equations Small-Signal Model
26
