asic design classification details

7/28/2019 ASIC design classification details

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ASIC


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Integrated Circuit Background

SSI (Small Scale Integration)

Less than 10 gates

Logic gates like 2 input NAND, XOR and other

standard low functionality ICs

MSI (Medium Scale Integration)

10 to 100 gates

ASICs, JK flip-flops, Counters and other standard

low functionality ICs

LSI (Large Scale Integration) 100 to 5000 gates

ASICs, Early microprocessors, Peripheral Interface

ICs etc.


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Integrated Circuit Background

VLSI (very large scale integration)

More than 5000 gates

Microprocessors, memory chips, ASICs

ULSI( Ultra Large Scale Integration) More than 50,000 (50K) gates

RAMS,VLIW processors. ULSI terminology is used

mostly in Japan


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The earliest ICs were based on the bipolar

transistor logic

They are classified as Transistor Transistor

Logic ICs (TTL) or as Emitter Coupled Logic

(ECL) ICs based on the circuit configuration.

The invention of Metal Oxide Silicon (MOS)

transistors in 1970 helped to reduce the

power consumption and cost of IntegratedCircuits.


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In 1980s-Aluminium gates of the MOS transistorsare replaced by polysilicon.

This enables to build NMOS and PMOS on thesame IC.

The introduction of CMOS (Complementary MetalOxide Silicon) technology in the 1980srevolutionized the Integrated Circuits.

The major advantages of the CMOS technologyare the reduced power consumption and highlevel of integration.


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The major advantages of using the ASICs are

Miniaturization: The usage of custom ICs will reduce the size of the endproduct. An ASIC may replace the functions of a number of PCBs in the

system, resulting in size reduction.

Lesser inventory: The reduced number of components per system reducesthe inventory. This in turn reduces the cash out flow.

Reduced cost and maintenance: Lesser components lead to fewer failuresand lesser system down time. Maintenance will be easy. All it may need

would be the replacement of a single PCB.

Lower power consumption: Lesser number of components in a systemreduces the power consumption. Most of the ASICs are based on the low

power CMOS technology.

Proprietary nature: Full protection from copycats. Your R&D investments

are well protected. Performance: More and more functions can be integrated to the ASIC,

without increasing the size or cost or power consumption of the product.


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The major Risks of using the ASICs are

Higher cost: ASIC will be always expensive than thestandard components. We will have to invest more time

and money for the design and development phase. Theselection of the ASIC technology is very important.

Time to market: The product lead time will be more for anASIC based system. The market research team should

define the requirement of the end product well in advance.Last minute changes in the specification will result in

delayed market entry and revenue loss. The right product

should be introduced in to the market at the right time.

First time success: The ASIC design should be properlysimulated and thoroughly tested to insure the first time

success. Any failure will affect the time to market and

resulting huge loss in revenue.


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An ASIC should be designed only if a functionally

equivalent standard, off the shelf. component is

not available from the market.

For example no engineer will design a memory

ASIC to be used in his system. Instead he will usethe standard components available from the

market.

Any IC that can be purchased by quoting a partnumber from the market is called a standard IC.


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By this definition we can treat all RAMS, ROMS,

Microprocessors, Counters, Flip-flops, Logic gates as

standard ICs. A standard IC will be always listed in the

data manual

An IC developed for a hand held game unit.

An IC used in a camera, an IC used in the smart card or

the like can be classified as ASIC products.

The ASIC part number will not be listed in the general DataManual. You will not be able to buy this product from the

open market against the part number.


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Application Specific Standard Product

(ASSP)

This is an ASIC designed to meet a specificapplication, but available from the market against a

part number.

This IC can not be classified as a standard product,

since it can not be used in different applications.

Some of the chips used in the PCs, modems,network controllers, remote controllers etc. can be

classified under ASSPs.


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TYPES OF ASICs Full-custom ASIC

Semi-custom ASIC

Cell-base ASIC

Gate-array-based ASIC

Programmable ASIC

Programmable LogicDevice (PLD)

Field-programmable

Gate array (FPGA)


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Engineer defines all or most of cells,circuits or layoutsfor that ASIC from scratch.

Designer has to define the characteristics of the cellsand circuits.

This technology is chosen if the existing cell libraries

- are not suitable for the particular design-are not fast

- consume more power

Most expensive design approach

Full custom technology is widely used in the mixedanalog digital ASICs.

FULL CUSTOM ASICs


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Standard-Cell-Based ASIC

Cell-based IC (CBIC-sea-bick) usespredesigned logic cells known as standardcells

Designer only defines the placement of thestandard cells and the interconnection.

Using a predesigned standard-cell library

reduced design risk and time Each standard cell can be optimized

individually


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Standard cell library includes

Sample logic gates. Functions like XOR,FF,ADDER, and

COMPARATORS,ALU.

Megafunctions like micropocessorcores,RAM core

The mega function blocks are sometime

known as fixed blocks.


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By selecting the CBIC technology, the designer

saves a lot of design and characterization timecompared to the Full Custom technology.

To customize the chip, the designer has to

define the floor planning and interconnects.

Like full custom design, since the placements of

the cells are done at the design phase, thefabrication of the ASIC has to go through all the

mask process


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asic design classification details

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