Integrated Circuits Lecture Notes

7/23/2019 Integrated Circuits Lecture Notes

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Integrated Circuits

Integrated Circuit (IC)

A thin chip consisting of at least two interconnected semiconductor devices, mainlytransistors, as well as passive components like resistors.

An electronic circuit where in all the elements of the circuit are integrated together ona single semiconductor substrate.

Fabrication Techniques

1) Film IC a technique for depositing passive circuit elements on an insulating substrate

a.Thin Film films with thickness less than approximately 100 microns, usuallydeposited through evaporation or sputtering.b. Thick Films produced by screening patterns of conducting and insulating

materials on ceramic substrates.

2) Monolithic IC a complete electronic circuit fabricated as an inseparable assembly of

circuit elements, mostly active ones, in a single small semiconductor structure. Itcannot be divided without permanently destroying its intended electronic

function. The physical properties of the semiconductor determine performance of

the circuit to a large degree. Usual means of production are through diffusion andepitaxial methods. Most common integrated circuits such as microprocessors,

memories, etc., are all monolithic.

3) Hybrid IC electronic circuit integrated on the ceramic substrate using various

components and then enclosed in the single package. The substrate does not

participate in the operation of the circuit, and connections between the

components are formed on its surface and some components such as resistors and

inductors may be fabricated directly onto it. Fabricated using diversifiedtechnologies, e.g. monolithic, thick film, etc., it has the advantage of design

flexibility; that is, they can be designed to provide wide use in specialized

applications, such as low-volume and high frequency circuits.

Packaging Techniques

To provide the necessary functions of interconnection, physical support,

environmental protection and heat dissipation, the whole IC must be surrounded by orencased in a package. Packages may be simple or they maybe complex-depending on the

nature of the device, the system of which it is a part and the environment in which the

device must operate.

The very surrounding of the IC with protective material, however, can degrade the

performance if the device, increase its physical size and weight, make testing the device

more difficult and decrease reliability. Moreover, the art of making the electronic


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package incur costs-which may be far higher than the cost of the active device itself.

Thus, the art of providing an effective electronic package becomes a complex balance ofproviding desired functions against constraints that may interact among themselves as

even further constraints.

Functions: Interconnection, Physical Support, Environment Protection and Heat

Dissipation

Constraints: Performance, Size, Weight, Testability, Reliability, and Cost

As a practical matter, the IC manufacturer must decide whether to package a given IC in

one or more standard packages (necessary for merchant sales) or develop one unique to

its needs (giving it a systems advantage over its competitors).

Packaging Examples

I. Surface Mount Technology (SMT) - a manufacturing process that attaches components

on the surface of the printed circuit board rather than inserting components intoplated-through holes, resulting in higher component density.A) Flat Pack - package with leads on two or four sides with either gull wing or flat

leads. Many types of IC flat packs are being produced in various sizes and

materials. These packages are available in square, rectangular, oval, and circular

configurations with 10 to 60 external leads. They may be made of metal, ceramic,

epoxy, glass, or combinations of those materials.


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Quad Flat Pack (QFP) - a fine-pitch package that is rectangular or square withgull-wing shaped leads on all four sides. The lead pitch of a QFP is typically

either 0.8mm or 0.65mm, although there are variations on this theme with smaller

lead pitches. Any of these packages can have a wide variety of lead counts from

44 leads on up to 240 or more. Variations are Ceramic (CQFP), Plastic (PQFP),

No Lead (NQFP), Thin (TQFP) and Very-thin (VQFP) or Low-profile (LQFP).

B) Chip Carrier - a low profile four-sided (rectangular) part package, whose

semiconductor chip cavity or mounting area is a large fraction of the chip size.They first came out as leadless chip carriers (LCC), which are a type of packaging

for integrated circuits that has no "leads", but instead rounded pins through the

edges of the ceramic package. However, by adding leads to the chip carrier, one

has less concern about thermal expansion mismatches.

C) Ball Grid Array (BGA) - A flip-chip type of package in which the internal die

terminals form a grid-style array, and are in contact with solder balls (or solder

bumps), which carry the electrical connection to the outside of the package. ThePCB footprint will have round landing pads to which the solder balls will besoldered when the package and PCB are heated in a reflow oven. Advantages of

the ball grid array package are that its size is compact and its leads do not get

damaged in handling (unlike the formed gull-wing leads of a QFP) and thus have

a long shelf life. Disadvantages of the BGA are they, or their solder joints, are

subject to stress-related failure (the intense vibration of rocket-powered space

vehicles can pop them right off the PCB); they can not be hand-soldered (they

require a reflow oven), making first-article prototypes a bit more expensive to

stuff; except for the outer rows, the solder joints can not be visually inspected andthey are difficult to rework.

D) Small Outline Integrated Circuit (SOIC) - a package with two parallel rows of 8-16 gull-wing leads protruding from its sides and has a lead pitch of 0.05 inches. It

occupies an area about 30 - 50% less than an equivalent DIP, with a typical

thickness that is 70% less. It is an excellent choice for maximum board density

and is ideal for the automotive, telecommunications, computer industries, or anyindustry that requires dense placement of chips on boards.

E) Thin Small Outline Package (TSOP) - package with two parallel rows of 20 to 48

gull-wing leads. This package is constructed using the latest low stress moldingcompounds and bonding technology to provide a package with total body

thickness of less then 1.90 mm and a pitch is 20 mils. This package is popular for

ROM applications in memory cards and other thin card applications. Variations

are Thin Shrink Small Outline Package (TSSOP) and Thin Very Small OutlinePackage (TVSOP).

II. Through-Hole Device (THD) - having pins designed to be inserted into holes and

soldered to pads on a printed board.A) Single In-line Package (SIP) - package which has one row of connecting pins. It is

not as popular as the dual in-line package, but has been used for packaging RAM

chips and multiple resistors with a common pin. Standard lead pitch is 0.100 inch.

B) Dual In-line Package (DIP) - package with two parallel rows of leads extendingfrom the base of the component. Standard lead pitch is 0.100 inch. Designed


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primarily to overcome the difficulties associated with handling and inserting

packages into mounting boards. DIPs are easily inserted by hand or machine andrequire no spreaders, spacers, insulators, or lead-forming tools. Standard hand

tools and soldering irons can be used to field-service the devices. A DIP is usuallyreferred to as a DIPn, where n is the total number of pins.

Plastic (PDIP) - although the least expensive DIP, it suffers from two majordrawbacks: poor thermal dissipation and poor moisture protection. To overcome

these drawbacks, hermetically sealed packages of several types are used. Also hasa Shrink Plastic DIP (SPDIP), a smaller version with 0.07-inch lead pitch.

Ceramic (CERDIP) - a sandwich structure with a ceramic base and lid bonded(with glass frit) to surround the lead frame assembly on which the chip ismounted. The lead frames must be bent before sealing, or the bending processwould shatter the glass seal.

C) Pin Grid Array (PGA) - The pin grid array or PGA is a type of packaging used

particularly in microprocessors. The IC is mounted in a ceramic slab of which one

face is covered, or partially covered, in a square array of metal pins. The pins can

then be inserted into the holes in a printed circuit board and soldered in place.

Standard lead pitch is 0.100 inch. For a given number of pins, this type of package

occupies less space than older types such as the DIP. The greatest concerns withpin grid packages are: special handling is required to prevent lead damage

(automatic insertion becomes a chilling thought for very high lead counts),

inspection of solder joints is difficult, and removal and replacement of soldered

units is very difficult because of the requirement and replacement of soldered

units is very difficult because of the requirement to heat the substrate uniformly

over a large area to effect release.

III. Chip-on-Board (COB) - in this technology integrated circuits are glued and wire-bonded directly to printed circuit boards instead of first being packaged. Theelectronics for many mass-produced toys are embedded by this system, which can be

identified by the black glob of plastic sitting on the board. Underneath that glob

(technical term: glob top), is a chip with fine wires bonded to both it and the landing

pads on the board.

IC Chip Categories

I. Level of Integration number of logic gates involved, the values given are normalindustry standards

A) Small-scale Integration (SSI) fewer than 12 logic gates. These were crucial toearly aerospace projects, and vice-versa. Both the Minuteman missile and Apollo

program needed lightweight digital computers for their inertially-guided flight

computers; the Apollo guidance computer led and motivated the integrated-circuittechnology, while the Minuteman missile forced it into mass-production.

B) Medium-scale Integration (MSI) 12 to 99 logic gates. Attractive economicallybecause while they cost little more to produce than SSI devices, they allowed


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more complex systems to be produced using smaller circuit boards, less assembly

work (because of fewer separate components), and a number of other advantages.C) Large-scale Integration (LSI) 100 to 999 logic gates. Began to be produced in

large quantities around 1970, for computer main memories and pocket calculators.D) Very large-scale Integration (VLSI) 10,000 to 99,999 logic gates. Made it

possible to fabricate a CPU on a single integrated circuit, to create a

microprocessor. This step was largely made possible by the codification of

"design rules" for the CMOS technology, which made production of working

devices much more of a systematic endeavor.

E) Ultra large-scale Integration (ULSI) 100,000 and more logic gates. Proposed forchips of complexity more than 1 million of transistors. However there is no

qualitative leap between VLSI and ULSI, hence normally in technical texts the

"VLSI" term covers ULSI as well, and "ULSI" is reserved only for cases when itis necessary to emphasize the chip complexity, e.g., in marketing.

F) Wafer-scale Integration (WSI) uses whole uncut wafers containing entirecomputers (processors as well as memory). Attempts to take this step

commercially failed, mostly because of defect-free manufacturability problems,and it does not now seem to be a high priority for industry.

G) System-on-Chip (SOC) a further advancement in manufacturing technology thatfollowed WSI in terms of IC complexity. In this approach, components

traditionally manufactured as separate chips to be wired together on a printedcircuit board, are designed to occupy a single chip that contains memory,

microprocessor(s), peripheral interfaces, Input/Output logic control, data

converters, etc., i.e., the whole electronic system.

II. Components used and device interconnectionA) Bipolar Contain parts comparable to discrete bipolar transistors, diodes,

capacitors, and resistors. Controlled by current applied to the control terminal

(base).They are the largest and formerly most popular digital IC family. They can

change states more than 20,000,000 times per second. Very inexpensive, but their

drawback is that they must be powered by a 5 volt supply, and they use a lot ofpower.

B) Metal-oxide semiconductors (MOS) Contain parts comparable to discretetransistors (NMOS, PMOS, and FETs). Source acts as the emitter; gate acts as the

base; and the drain acts as the collector. Controlled by voltage produced on the

controlling terminal (gate).P and N channels MOS contain more gates per chip than TTL. These

make many special purpose chips, like microprocessors, memories, etc. Their

drawbacks are: few counterparts to popular TTL chips, they're slower than TTL

chips, and some require two or more supply voltages. They may also be damaged

by static electricity. Complementary MOS, or CMOS, are the most versatile

digital IC family. There are CMOS versions of most popular TTL chips. Most

CMOS has a wide supply voltage range, typically from +3 to +18 V. It uses less

power than any other digital IC family. Its drawbacks are that it can be damaged

by static electricity.


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C) Combination technology ICs that combine technologies are able to obtain theadvantages from each technology.1. BIFET Bipolar FET2. BIMOS Bipolar MOS3. BIDFET high voltage bipolar field-effect transistor; MOS technology added

to the BIFET approach.

4. BIDMOS diffused metal-oxide semiconductor (DMOS) and bipolartechnology

5. Lin CMOS silicon gate MOSFETs. Allows for linear and digital logic on thesame IC.

III. Application

A) Digital Circuits a circuit whose step-function input voltage causes its output tochange in a step-function manner from a specific value of voltage to another. The

transition between the two voltage values is accomplished in essentially zero time.Each voltage level of this two-state circuit can represent a particular state, such as:

ON/OFF, ZERO/ONE, TRUE/FALSE, HIGH/LOW, MARK/SPACE, or anyother predetermined condition. They are implemented through Combinational

logic circuits, which has basic logic gates as its basic building blocks, and

Sequential logic circuits, which use flip-flops as its basic building blocks.

1. Decision-making Functions consist mainly of combinational gates. For everycombination of bits in the various input wires, there is a definite, prearranged

combination in the output wires to be decided upon. The output combination

is the same every time a particular input combination occurs. Gates are

grouped together in various combinations to form the decision-making

circuits.a. Code converter circuits capable of encoding data to a usable form for the

computer and decoding the data so it can be displayed or used by a

peripheral.b. Data routing circuits routes data inside the computer from various sources

to various destinations where they can be processed.

Adder / Subtractor

Command signals (enables)

Comparator

Multiplexer / Demultiplexer

Selectors

Translators2. Memory-type Functions store information derived from previous

combinations of inputs, so the combination of output bits depends not only onthe input signals at the moment, but also on previous combinations of bits.

These memory-type circuits are called sequential circuits.

a. Counters used to count operations, quantities, and periods of time; or for

addressing information in storage.

b. Registers built simply by combining groups of flip-flops to act as a unit.

The length of a register corresponds to the number of bits or flip-flopswithin this grouping. A register must be able to receive information from


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one or more sources, preserve the information without alteration until it is

needed and deliver the information to one or more destinations when it isrequired.

B) Analog Circuits electronic circuits sense, measure, monitor, modify, amplify,operate, and control changing conditions. Circuits in which the output voltagevaries as a continuous function of its input, they include no digital activity and

encompass both linear and non-linear analog functions.

1. Linear circuits amplifying-type circuits in integrated form. A linear circuit is

one whose output voltage is proportional to its input voltage, generally, over a

clearly defined range of input voltage, output voltage, and frequency. The

degree of deviation of the output voltage of a linear circuit from a proportional

response to its input voltage is called "distortion".

a. Operational Amplifier The basic gate for a linear IC, its function is toincrease the power, current, or voltage applied to its inputs. The op amp

was originally designed to perform mathematical operations, such asaddition, subtraction, integration, and differentiation and derives its name

from these operations. The circuit is now included in a considerablybroader range of applications.

b. Audio Amplifier in an audio system, sound coming from a source is

converted to analog voltage variations. These signals are then amplified by

the first linear audio amplifier section (pre-amplifier), whose output is tooweak, is coupled to a second linear audio amplifier section (power

amplifier), further amplifying the signal to provide enough power to drive

the loudspeaker.

2. Non-linear circuits although a linear circuit can be referred to as an analog

circuit, an analog circuit is not necessarily a linear circuit. Some analogcircuits are specifically designed to provide an output voltage that is not

proportional to its input, even though the output will vary as a function of the

changing input voltage.a. Voltage Regulator convert a voltage applied to their input into a fixed or

variable voltage. Most voltage regulators are installed in packages made of

metal or having metal tabs to help radiate excessive heat into thesurrounding air.

b. Comparator basically a high gain amplifier without feedback that

compares the level of the changing analog voltage at its input to a

reference voltage. When the changing analog voltage has reached the

reference voltage, a digital output voltage change appears at its outputC) Interface Circuits As digital ICs are replacing the more traditional analog ICs,

the need for electronic circuits that will effectively convert from one technique to

the other is rapidly intensifying. To meet this need, IC manufacturers have been

producing more precise, faster, smaller, low power consumption, and less

expensive converter circuits.

Analog-to-Digital Converter

Digital-to-Analog Converter

IV. Digital Logic Families


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A) Saturation Logic Families slow but has low power dissipation1. Resistor-Transistor Logic (RTL)

Utilizes resistors and bipolar junction transistors as circuit elements

Uses NOR gates as the standard gate

Main limitation is limited fan-in, usually 3 inputs being the limit before itcompletely lost usable noise immunity

Simple and inexpensive but is already obsolete

2. Diode-Transistor Logic (DTL)

Utilizes diodes, resistors and BJTs as circuit elements

Uses NAND gate as the standard gate

More resilient to noise than RTL but also obsolete3. High Level Diode-Transistor Logic (HDTL)

Higher power supply voltage than DTL, usually powered by 25V instead

of 5V Widely used in industry where machinery causes electrical noise and there

are large power line transients4. Transistor-Transistor Logic (TTL)

Most widely used packaged IC

Feature a multiple-emitter input transistor for fast switching speeds

Uses NAND gate as the standard gate

Faster than CMOS but consumes more power

Often called bipolar since its logic gates use BJTs

Variations of the TTL family includea. L Family (low power) slowest but has the least power consumption

since its resistance values are higher than the standard TTLb. H Family (high power) high speed but also suffer high power

consumption due to complex circuitry

c. S Family (Schottky) uses Schottky diodes on the base of the transistor

to keep them out of saturation

d. LS Family (low power Schottky) has higher resistance so the speed

decreased but the power dissipation dropped

e. AS Family (advanced Schottky) utilizes Schottky barrier diodes

clamped transistor, fastest among the the TTL family with lower

power dissipation than the standard TTLf. ALS Family (advanced low power Schottky) third fastest and the

second least power consumptionB) Current Mode Logic Families fast but high power dissipation

1. Emitter-Coupled Logic (ECL)

Has the fastest switching speeds compared to any logic ICs since itstransistors are configured to act as difference-amplifier emitter followers

that are never saturated

Consumes more power than TTL

SSI and MSI level

Eliminates turn-off delay


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Input logic levels are limited to a narrow voltage range to reduce the largerpower dissipation resulting from active mode

Also called Current-Mode Logic (CML), being the first of its family2. Integrated-Injection Logic (IIL or I2L)

Low power, high density logic family suitable for LSI and VLSIimplementation

Operates by saturating one or more input transistors

Power dissipation is reduced by limiting the logic levels to saturationvoltages

Combines the low voltage swing of the ECL family and the saturation ofthe RTL to achieve the goal of high density at low power

Also known as Merged Transistor Logic (MTL)3. Complementary Metal-oxide Semiconductor (CMOS)

Uses p-channel and n-channel MOS transistors which consume the leastpower but at reduced speed

Only uses significant power when its transistors are switching between onand off states

Allows a high density of logic functions on a chip

Can operate with variable power supply, from +3 to +18V

Variations include CD (CMOS Digital), TTLC (Bipolar TTL series inCMOS technology), QMOS (Quick MOS) and HMOS (High-Speed MOS)

Integrated Circuits Lecture Notes

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