microelettronica cmos theory lezione 2. cmos vlsi design1: circuits & layoutslide 2 outline a...

48
MICROELETTRONICA CMOS THEORY Lezione 2

Upload: terry-applegate

Post on 31-Mar-2015

225 views

Category:

Documents


2 download

TRANSCRIPT

Page 1: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

MICROELETTRONICA

CMOS THEORY

Lezione 2

Page 2: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 2CMOS VLSI Design

Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches & Flip-Flops Standard Cell Layouts Stick Diagrams

Page 3: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 3CMOS VLSI Design

Invention of the Transistor Vacuum tubes ruled in first half of 20th century Large,

expensive, power-hungry, unreliable 1947: first point contact transistor

– John Bardeen and Walter Brattain at Bell Labs– Read Crystal Fire

by Riordan, Hoddeson

Page 4: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 4CMOS VLSI Design

Transistor Types Bipolar transistors

– npn or pnp silicon structure– Small current into very thin base layer controls

large currents between emitter and collector– Base currents limit integration density

Metal Oxide Semiconductor Field Effect Transistors– nMOS and pMOS MOSFETS– Voltage applied to insulated gate controls current

between source and drain– Low power allows very high integration

Page 5: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 5CMOS VLSI Design

1970’s processes usually had only nMOS transistors– Inexpensive, but consume power while idle

1980s-present: CMOS processes for low idle power

MOS Integrated Circuits

Intel 1101 256-bit SRAM Intel 4004 4-bit Proc

Page 6: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 6CMOS VLSI Design

CMOS Gate Design Activity:

– Sketch a 4-input CMOS NAND gate

Page 7: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 7CMOS VLSI Design

CMOS Gate Design Activity:

– Sketch a 4-input CMOS NOR gate

A

B

C

DY

Page 8: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 8CMOS VLSI Design

Complementary CMOS Complementary CMOS logic gates

– nMOS pull-down network– pMOS pull-up network– a.k.a. static CMOS

pMOSpull-upnetwork

outputinputs

nMOSpull-downnetwork

Pull-up OFF Pull-up ON

Pull-down OFF Z (float) 1

Pull-down ON 0 X (crowbar)

Page 9: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 9CMOS VLSI Design

Series and Parallel nMOS: 1 = ON pMOS: 0 = ON Series: both must be ON Parallel: either can be ON

(a)

a

b

a

b

g1

g2

0

0

a

b

0

1

a

b

1

0

a

b

1

1

OFF OFF OFF ON

(b)

a

b

a

b

g1

g2

0

0

a

b

0

1

a

b

1

0

a

b

1

1

ON OFF OFF OFF

(c)

a

b

a

b

g1 g2 0 0

OFF ON ON ON

(d) ON ON ON OFF

a

b

0

a

b

1

a

b

11 0 1

a

b

0 0

a

b

0

a

b

1

a

b

11 0 1

a

b

g1 g2

Page 10: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 10CMOS VLSI Design

Conduction Complement Complementary CMOS gates always produce 0 or 1 Ex: NAND gate

– Series nMOS: Y=0 when both inputs are 1– Thus Y=1 when either input is 0– Requires parallel pMOS

Rule of Conduction Complements– Pull-up network is complement of pull-down– Parallel -> series, series -> parallel

A

B

Y

Page 11: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 11CMOS VLSI Design

Compound Gates Compound gates can do any inverting function Ex: (AND-AND-OR-INVERT, AOI22)Y A B C D

A

B

C

D

A

B

C

D

A B C DA B

C D

B

D

YA

CA

C

A

B

C

D

B

D

Y

(a)

(c)

(e)

(b)

(d)

(f)

Page 12: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 12CMOS VLSI Design

Example: O3AI Y A B C D

Page 13: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 13CMOS VLSI Design

Example: O3AI Y A B C D

A B

Y

C

D

DC

B

A

Page 14: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 14CMOS VLSI Design

Signal Strength Strength of signal

– How close it approximates ideal voltage source VDD and GND rails are strongest 1 and 0

nMOS pass strong 0– But degraded or weak 1

pMOS pass strong 1– But degraded or weak 0

Thus nMOS are best for pull-down network

Page 15: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 15CMOS VLSI Design

Pass Transistors Transistors can be used as switches

g

s d

g = 0

s d

g = 1

s d

0 strong 0

Input Output

1 degraded 1

g

s d

g = 0

s d

g = 1

s d

0 degraded 0

Input Output

strong 1

g = 1

g = 1

g = 0

g = 0

Page 16: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 16CMOS VLSI Design

Transmission Gates Pass transistors produce degraded outputs Transmission gates pass both 0 and 1 well

Page 17: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 17CMOS VLSI Design

Transmission Gates Pass transistors produce degraded outputs Transmission gates pass both 0 and 1 well

g = 0, gb = 1

a b

g = 1, gb = 0

a b

0 strong 0

Input Output

1 strong 1

g

gb

a b

a b

g

gb

a b

g

gb

a b

g

gb

g = 1, gb = 0

g = 1, gb = 0

Page 18: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 18CMOS VLSI Design

Tristates Tristate buffer produces Z when not enabled

EN A Y

0 0 Z

0 1 Z

1 0 0

1 1 1

A Y

EN

A Y

EN

EN

Page 19: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 19CMOS VLSI Design

Nonrestoring Tristate Transmission gate acts as tristate buffer

– Only two transistors– But nonrestoring

• Noise on A is passed on to Y

A Y

EN

EN

Page 20: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 20CMOS VLSI Design

Tristate Inverter Tristate inverter produces restored output

– Violates conduction complement rule– Because we want a Z output

A

YEN

EN

Page 21: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 21CMOS VLSI Design

Tristate Inverter Tristate inverter produces restored output

A

YEN

A

Y

EN = 0Y = 'Z'

Y

EN = 1Y = A

A

EN

Page 22: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 22CMOS VLSI Design

Multiplexers 2:1 multiplexer chooses between two inputs

S D1 D0 Y

0 X 0

0 X 1

1 0 X

1 1 X

0

1

S

D0

D1Y

Page 23: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 23CMOS VLSI Design

Multiplexers 2:1 multiplexer chooses between two inputs

S D1 D0 Y

0 X 0 0

0 X 1 1

1 0 X 0

1 1 X 1

0

1

S

D0

D1Y

Page 24: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 24CMOS VLSI Design

Gate-Level Mux Design How many transistors are needed?

1 0 (too many transistors)Y SD SD

Page 25: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 25CMOS VLSI Design

Gate-Level Mux Design How many transistors are needed? 20

1 0 (too many transistors)Y SD SD

44

D1

D0S Y

4

2

2

2 Y2

D1

D0S

Page 26: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 26CMOS VLSI Design

Transmission Gate Mux Nonrestoring mux uses two transmission gates

Page 27: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 27CMOS VLSI Design

Transmission Gate Mux Nonrestoring mux uses two transmission gates

– Only 4 transistorsS

S

D0

D1

YS

Page 28: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 28CMOS VLSI Design

Inverting Mux Inverting multiplexer

– Use compound AOI22– Or pair of tristate inverters– Essentially the same thing

Noninverting multiplexer adds an inverter

S

D0 D1

Y

S

D0

D1Y

0

1S

Y

D0

D1

S

S

S

S

S

S

Page 29: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 29CMOS VLSI Design

4:1 Multiplexer 4:1 mux chooses one of 4 inputs using two selects

Page 30: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 30CMOS VLSI Design

4:1 Multiplexer 4:1 mux chooses one of 4 inputs using two selects

– Two levels of 2:1 muxes– Or four tristates

S0

D0

D1

0

1

0

1

0

1Y

S1

D2

D3

D0

D1

D2

D3

Y

S1S0 S1S0 S1S0 S1S0

Page 31: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 31CMOS VLSI Design

D Latch When CLK = 1, latch is transparent

– D flows through to Q like a buffer When CLK = 0, the latch is opaque

– Q holds its old value independent of D a.k.a. transparent latch or level-sensitive latch

CLK

D Q

Latc

h D

CLK

Q

Page 32: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 32CMOS VLSI Design

D Latch Design Multiplexer chooses D or old Q

1

0

D

CLK

QCLK

CLKCLK

CLK

DQ Q

Q

Page 33: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 33CMOS VLSI Design

D Latch Operation

CLK = 1

D Q

Q

CLK = 0

D Q

Q

D

CLK

Q

Page 34: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 34CMOS VLSI Design

D Flip-flop When CLK rises, D is copied to Q At all other times, Q holds its value a.k.a. positive edge-triggered flip-flop, master-slave

flip-flop

Flo

p

CLK

D Q

D

CLK

Q

Page 35: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 35CMOS VLSI Design

D Flip-flop Design Built from master and slave D latches

QM

CLK

CLKCLK

CLK

Q

CLK

CLK

CLK

CLK

D

Latc

h

Latc

h

D QQM

CLK

CLK

Page 36: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 36CMOS VLSI Design

D Flip-flop Operation

CLK = 1

D

CLK = 0

Q

D

QM

QMQ

D

CLK

Q

Page 37: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 37CMOS VLSI Design

Race Condition Back-to-back flops can malfunction from clock skew

– Second flip-flop fires late– Sees first flip-flop change and captures its result– Called hold-time failure or race condition

CLK1

D Q1

Flo

p

Flo

p

CLK2

Q2

CLK1

CLK2

Q1

Q2

Page 38: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 38CMOS VLSI Design

Nonoverlapping Clocks Nonoverlapping clocks can prevent races

– As long as nonoverlap exceeds clock skew We will use them in this class for safe design

– Industry manages skew more carefully instead 1

11

1

2

22

2

2

1

QMQD

Page 39: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 39CMOS VLSI Design

Gate Layout Layout can be very time consuming

– Design gates to fit together nicely– Build a library of standard cells

Standard cell design methodology

– VDD and GND should abut (standard height)

– Adjacent gates should satisfy design rules– nMOS at bottom and pMOS at top– All gates include well and substrate contacts

Page 40: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 40CMOS VLSI Design

Example: Inverter

Page 41: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 41CMOS VLSI Design

Example: NAND3 Horizontal N-diffusion and p-diffusion strips Vertical polysilicon gates Metal1 VDD rail at top

Metal1 GND rail at bottom 32 by 40

Page 42: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 42CMOS VLSI Design

Stick Diagrams Stick diagrams help plan layout quickly

– Need not be to scale– Draw with color pencils or dry-erase markers

Page 43: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 43CMOS VLSI Design

Wiring Tracks A wiring track is the space required for a wire

– 4 width, 4 spacing from neighbor = 8 pitch Transistors also consume one wiring track

Page 44: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 44CMOS VLSI Design

Well spacing Wells must surround transistors by 6

– Implies 12 between opposite transistor flavors– Leaves room for one wire track

Page 45: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 45CMOS VLSI Design

Area Estimation Estimate area by counting wiring tracks

– Multiply by 8 to express in

Page 46: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 46CMOS VLSI Design

Example: O3AI Sketch a stick diagram for O3AI and estimate area

– Y A B C D

Page 47: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 47CMOS VLSI Design

Example: O3AI Sketch a stick diagram for O3AI and estimate area

– Y A B C D

Page 48: MICROELETTRONICA CMOS THEORY Lezione 2. CMOS VLSI Design1: Circuits & LayoutSlide 2 Outline A Brief History CMOS Gate Design Pass Transistors CMOS Latches

1: Circuits & Layout Slide 48CMOS VLSI Design

Example: O3AI Sketch a stick diagram for O3AI and estimate area

– Y A B C D