Ramesh CoreEL VLSI VSAT Module1 2 [Compatibility Mode]

8/16/2019 Ramesh CoreEL VLSI VSAT Module1 2 [Compatibility Mode]

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VLSI VSAT Program

CoreEL University Program Team


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Contents

Introduction to Physical Design- Layout

ASIC Construction : Floorplanning, Placement &Routing ;

Physical verification: DRC, LVS

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Basics of Digital CMOS Design


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Design flow in VLSI / FPGA

Specifications

Design Entry

Functional Verification

S nthesis

Graphical

Simulation

S nthesizer

ASIC Specific

Flow

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Post-Synthesis Verification

PAR

Post-PAR Verification

Bit-Format

Post-syn simulation

Simulation

Verification

Layout

Fabrication

Verification

Physical Verification

Formal Verification

Layout Editor


Confidential


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Introduction to Physical Design

Basics of Layout Designing : Design Kits,

Standard Cells.

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Confidential


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Basics of Chip Designing

Foundry

Designer

GDS II

Design Kit

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(Fabricator)

CoreEl confidential

Chip

GDS = Graphic Database SystemIts the de facto industry standard for data exchange of IC layout artwork.

TSMC,UMC,Faraday, etc


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Transistors

a) Circuit Symbol b) Physical Realization

GateSource

DrainGate

SourceDrain

Bulk

Width

Length

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c) Layout View

Minimum Length=2λ

Width=4λSource Drain

Gate

d) Simple RC Model

Gate

Drain

Source

Cdrain

Csource

Ron

Cgate

Confidential


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Files in Design Kit

Library Database: Layout, schematic, symbol, abstract, andother logical or simulation views.

Timing Abstract - provides functional definitions, timing,ower, and noise information for each cell

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DRC, LVS, PEX rule files.

Technology files: Layer specifications

Confidential


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Cell List in Digital Design Kit

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Comparison General definitionmodule mux1( select, d, q );

input[1:0] select;

input[3:0] d;

output q;

Synthesized Code

// Verilog description for cell mux1,

// LeonardoSpectrum Level 3,

2010a.7

module mux1 ( select, d, q ) ;

input [1:0]select ;

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w re q;

wire[1:0] select;

wire[3:0] d;

assign q = d[select];

endmodule

output q ;

wire nx59, nx61;

mux21 ix23 (.Y (q), .A0 (nx59),

.A1 (nx61), .S0 (select[1])) ;

mux21 ix60 (.Y (nx59), .A0 (d[0]),.A1 (d[1]), .S0 (select[0])) ;

mux21 ix62 (.Y (nx61), .A0 (d[2]),

.A1 (d[3]), .S0 (select[0])) ;

endmodule

Confidential


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Design Kit

Digital Design Kit

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Standard Cells



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ASIC Backend Flow

System Partitioning: Divide Large system intoASIC-sized Pieces

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Floorplan: Arrange the blocks of the netlist onthe chip

Placement : Decide the location of cells in ablock

Confidential


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Floorplan

The input to a floorplanning tool is a hierarchical netlist thatdescribes the interconnection of the blocks

The goals of floorplanning are to:

arrange the blocks on a chip,

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decide the location and number of the power pads,

decide the type of power distribution, and

decide the location and type of clock distribution

Confidential


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Placement

The goal of a placement tool is to arrange all the logic cellswithin the flexible blocks on a chip

Goals:

r n h r r n m l h r in

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Minimize all the critical net delays

Make the chip as dense as possible

Confidential


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Placement Algorithms

Two Types of Algorithms used:

Min-cut algorithm

Eigenvalue method

-

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Confidential


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Algorithms

Min-Cut Algorithm Cut the placement area into two pieces.

Swap the logic cells to minimize the cut cost.

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epeat t e process rom step , cutt ng sma er p ecesuntil all the logic cells are placed.

Confidential


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Routing

Process of placing and connecting signal and powerpaths between the standard cells or blocks



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Global & Detailed Routing

Global Routing A global router does not make any connections, it just

plans them.

The objectives of global routing are

Minimize the total interconnect length.

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complete the routing.

Minimize the critical path delay.

Detailed Routing The detailed router decides the exact location and

layers for each interconnect.

Confidential


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Special Routing

Clock Routing :

Uses Higher metal Layer (has less resistance & capacitance )

Power Routing:

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• Each of the power buses has to be sized according to thecurrent it will carry.

• The required power-bus widths can be estimated

automatically from library information.

Confidential


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Design flow in VLSI / FPGA

Specifications

Design Entry

Functional Verification

S nthesis

Graphical

Simulation

S nthesizer

ASIC Specific

Flow

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Post-Synthesis Verification

PAR

Post-PAR Verification

Bit-Format

Post-syn simulation

Simulation

Verification

Layout

Fabrication

Verification


Formal Verification

Layout Editor


Confidential


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References

Application Specific Integrated Circuits-- By Smith– Pearson Publication

http://iroi.seu.edu.cn/books/asics/asics.htm#anchor11320

Physical design essentials: an ASIC design implementation perspective-

- By Khosrow Golshan– Springer Publication

Algorithms for VLSI Design Automation-- By Gerez– Wiley India Edition

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VLSI physical design automation: theory and practice– By Sadiq M. Sait,

Habib Youssef– World Scientific.

Introduction to Place and Route Design in Vlsis-- By Patrick Lee

CMOS: Circuit Design, Layout, and Simulation-- By R. Jacob Baker

Confidential


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Physical Verification & PEX

Physical Verification DRC

LVS

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Confidential


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Physical Verification : DRC & LVS

DRC : Design Rule CheckingInputs: Layout -- GDSII, OASIS, etc.

Rule File

OutputsDRC ResultsReport

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: ayou ersus c ema cInputsLayout -- GDSII, OASIS, etc.Logic (for LVS) i.e SPICE / Verilog

Rule FileOutputs

LVS ResultsReport

Confidential


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DRC Errors

Internal

Width:INT oxide


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LVS (Layout Vs Schematic)

RESET

S

D

G

Design View

• Design Architect• Composer

S

RESET

D

G Layout View• DESIGNrev• Virtuoso• StreamView

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DeviceExtraction

ConnectivityExtraction

SchematicCompilation

HDLCompilation

VERIFICATIONRESULTS

COMPARISONPHASE

LAYOUT NETLIST SOURCE NETLIST

Confidential


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LVS Rule File

Device Statements

E.g. device r(pl) rpoly ipoly ipoly [20000]

Gate Recognition Statements LVS GROUND NAME VSS VSS1

LVS POWER NAME VDD VCC

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LVS RECOGNIZE GATES ALL Connectivity Statements

CONNECT metal1 metal2 BY via12

VIRTUAL CONNECT NAME vdd

Confidential


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Shorts and Opens

Short circuits

Occur when nets that should be isolated are connected

Can lead to a difference between the number of nets:

# layout nets < # source nets

Open circuits

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entire length of a layout net Can lead to a difference between the number of nets:

# layout nets > # source nets

Confidential


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Device

NET Y

ELEMENT = MN

M2

S

D

G

1. LVS defines the MNelement templatebased upon theDevice statement.

// Device StatementDEVICE MN NGATE POLY NSD NSD PWELL [0]

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LAYER PWELL 1LAYER OXIDE 2LAYER POLY 4LAYER NPLUS 5

PAREA = OXIDE AND PWELLNGATE = POLY AND PAREANOX = OXIDE AND NPLUSNSD = NOX NOT NGATE

Confidential


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Parasitic Extraction

Extracts the parasitic values of each interconnect, via, andcontact that will be on the silicon wafer

Parasitic Formats: SPF, RPF and DSPF

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delay and loading due to parasitic resistance andcapacitance.

RSPF– Reduced SPF.

DSPF--- Detailed SPF , describes the actual parasiticresistance and capacitance components of a net.

Confidential


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Physical Verification Flow using Calibre

Calibre LVS-H

LayoutGDSII

Sourcenetlist

Rule fileHcell list(optional)

Netlist extraction

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Extractionreport

Extractednetlist

LVSreport svdb

Locate errors usingCalibre RVE & Layout tool

Fix layouterrors

Confidential


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References

Physical design essentials: an ASIC design implementationperspective-- By Khosrow Golshan– Springer Publication

http://www.mentor.com/products/ic_nanometer_design/verification-signoff/physical-verification/

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IC mask design: essential layout techniques-- byChristopher Saint, Judy Saint

CMOS: Circuit Design, Layout, and Simulation-- By R.Jacob Baker

Confidential


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Basics of Digital CMOS Design

Basic Working of CMOS logic

Models of Digital Design

Pass Gate

Transmission Gate

Inverter

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Switching Characteristics

Sizing

Logic Effort

Types of Logic Circuits

Confidential


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Complementary CMOS

Complementary CMOS logic gates

nMOS pull-down network

pMOS pull-up network

a.k.a. static CMOSpMOSpull-upnetwork

output

inputs

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nMOSpull-downnetworkPull-up OFF Pull-up ON

Pull-down OFF Z (float) 1

Pull-down ON 0 X (crowbar)

Confidential


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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

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(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

Confidential


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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 pMOSA

Y

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Rule of Conduction Complements

Pull-up network is complement of pull-down

Parallel -> series, series -> parallel

B

Confidential


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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

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pMOS pass strong 1 But degraded or weak 0

Thus nMOS are best for pull-down network

Confidential


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Why NMOS is week 1?

The nMOS transistor will stop conducting if VGS < VT.Let VT = 0.7V,


As source goes from 0V 5V, VGS goes from 5V 0V.

When VS > 4.3V, then VGS < VT, so switch stopsconducting.VD left at 5V - VT = 5V - 0.7V = 4.3V or Vdd - VT.


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Pass Transistors

Transistors can be used as switches

g

s d

g = 0s d

g = 1

0 strong 0Input Output

g = 1

g = 1

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s 1 degraded 1

g

s d

g = 0

s d

g = 1s d

0 degraded 0

Input Output

strong 1

g = 0

g = 0

Confidential


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Transmission Gates

Pass transistors produce degraded outputs

Transmission gates pass both 0 and 1 well



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Transmission Gates

Pass transistors produce degraded outputs

Transmission gates pass both 0 and 1 well

g = 0, gb = 1

Input Output

g g = 1, gb = 0

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g = 1, gb = 0

a b

s rong

1 strong 1gb

a b

a b

g

gb

a b

g

gb

a b

g

gb

g = 1, gb = 0

Confidential


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CMOS Inverter

VDD

PMOS2λλλλ

V DD

PMOS Contacts

N Well

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Polysilicon

InOut

GND

Metal 1

NMOS

NMOS

Confidential

V I Ch i i C


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V-I Characteristic Curve

I Dn

V in = 2.5

V in

= 2

V in

= 0

V in

= 0.5 NMOSPMOS


V out

V in

= 1.5V in

= 1

V in

= 0

V in = 0.5

V in

= 1V in = 1.5

V in = 2

V in

= 2.5

V in = 1V

in = 1.5

CMOS I VTC C


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CMOS Inverter VTC Curve

V out

1 .

5

2

2 .

5

NMOS sat

NMOS off

PMOS res

NMOS sat

PMOS res


V in0.5 1 1.5 2 2.5

0 .

5

1

NMOS resPMOS off

NMOS res

PMOS sat

S it hi Ch t i ti


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Switching Characteristics

Define: Rise time tr = time required for a node to charge from the 10% point to 90% point

Fall time tf = time required for a node to discharge from 90% to 10% point

Delay time td = delay from the 50% point on the input to the 50% point on theoutput

Falling delay tdf = delay time with output falling Rising delay tdr = delay time with output rising


N i M i


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Noise Margin

Noise margin = voltage difference between output of onegate and input of next. Noise must exceed noise margin tomake second gate produce wrong output.


I t Si i


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Inverter Sizing


In each case, the rise or fall time depends on the channelresistance, which in-turn, depends on the devicedimensions.

Gate Delay Components


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Gate Delay Components

Split delay of logic gate into three componentsDelay = Logical Effort x Electrical Effort + Parasitic Delay

Logic Gate

Cin

Cout

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Complexity of logic function (Invert, NAND, NOR, etc) Define inverter has logical effort = 1 Depends only on topology not transistor sizing

Electrical Effort Ratio of output capacitance to input capacitance Cout /Cin

Parasitic Delay Intrinsic self-loading of gate Independent of transistor sizes and output load

Confidential

Method of Logical Effort


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Method of Logical Effort

Easy way to estimate delays in CMOS process Indicates correct number of logic stages to use and

transistor sizes

Characterize process speed with single delay parameter: ττ, delay of inverter driving same-sized inverter (no parasitic)


Logical Effort for Simple Gates


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Logical Effort for Simple Gates Define Logical Effort of Inverter = 1

For other gates, size to give same current drive as inverter

Logical Effort is ratio of logic gate’s input cap. to inverter’s input cap.

Relative2 2 4

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Widths

InverterInput Cap = 3 units

L.E.=1 (definition)

NANDInput Cap = 4 units

L.E.=4/3

NORInput Cap = 5 units

L.E.=5/3

2

1

2

2 1

4

1

Confidential

(n+2)/3

Logic Blocks


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Logic Blocks


F = AB (C +D )

N-block implementation of a Boolean functionA series of N connection P(A,B)= AB;A parallel of N Connection P(A,B)= A+B;

CMOS Tristate & Buffer


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CMOS Tristate & BufferTristate CMOS Buffer


X C output

0 0 High Z0 1 1

1 0 High Z

1 1 0

When long lines or chip outputsmust be driven buffer circuits,

which have the advantage thatthe output driving transistors aredirectly connected to the outputand ground or respectively



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Static CMOS

Dynamic CMOS

Pseudo NMOS

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Pass Transistor Logic

Confidential

Static CMOS


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Static CMOS


Characteristics•At every point in time, each gate output is connected to either Vdd or Vss via alow-resistance path•It have rail-to-rail swing , no static power dissipation•Speed depends on the transistor sizing and parasitic that are involved with it.Disadvantage

•The problem with this type of implementation is that for N fan-in gate 2N number of transistors are required, ie, more area required to implement logic.This has an impact on the capacitance and thus the speed of the gate.

Dynamic CMOS


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Dynamic CMOS


Characteristics•Dynamic CMOS circuits rely on the temporary storage of signal values on thecapacitance of high-impedance circuit nodes.•no static power dissipation.

•Disadvantage•the need for repeated charging and discharging even when the inputs do notchange their state.

Buffered dynamic CMOS (domino) logic

Pseudo NMOS


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Pseudo NMOS


Characteristics•The advantage of pseudo-NMOS logic are its high speed and low transistorcount.

Disadvantage

•Static power consumption of the pull-up transistor as well as the reducedoutput voltage swing and gain, which makes the gate more susceptible tonoise.



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Characteristics•The advantages of pass-transistor logic are

the simple design, the reuse of alreadyavailable signals.•Low contribution to static power.

Disadvantage•Output levels can be no higher than the input

level

Four-to-one multiplexer in pass-transistor logic

References


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References

CMOS: Circuit Design, Layout, and Simulation-- By R. Jacob Baker

CMOS Digital Integrated Circuits-- By Sung-Mo Kang, Yusuf Leblebici

CMOS logic circuit design-- By John Paul Uyemura Cmos Vlsi Design: A Circuits And Systems Perspective, 3/E-- By Weste,

Weste Neil H.E.

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Douglas A. Pucknell and Kamran Eshraghian, Basic VLSI Design, Third

Edition

http://www.iue.tuwien.ac.at/phd/schrom/node93.html

Confidential


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Thank You


[email protected]

Documents

Ramesh CoreEL VLSI VSAT Module1 2 [Compatibility Mode]