ComputerScience: Integrated Circuit Coding / Numbering

Tuesday, October 4, 2011

Integrated Circuit Coding / Numbering

Introduction to Integrated Circuits(IC’s)

An integrated circuit can be defined generally as an arrangement of multifunction semiconductor devices. It consists of a single-crystal chip of silicon, nearly 1.5 mm² in cross-section, containing both active and passive elements and their interconnections.

Earlier electronic circuits were assembled from individual components (e.g. resistor, capacitor, diode, transistors etc.) joined by wires. The sizes were further reduced by the use of printed circuit boards. The interconnection between various components is made through their metal strips formed on an insulating sheet. Such circuits are known as discrete circuits because each component of the circuit is separate from others. Main disadvantages of discrete circuits are that

they occupy large space
large number of soldered joints are less reliable

In an integrated circuit, various components such as resistors, capacitors, diodes etc. are fabricated on the same semiconductor chip. The reliability of the circuit is increased as the active and passive components are built in the same crystal. The most noticeable characteristic of an IC is its size. It is thousands of times smaller than a semiconductor structure built in the usual manner with discrete components

Our world is full of integrated circuits. You find several of them in computers. For example, the microprocessor is an integrated circuit that processes all information in the computer. It keeps track of what keys are pressed and if the mouse has been moved. It counts numbers and runs programs, games and the operating system. Integrated circuits are also found in almost every modern electrical device such as cars, television sets, CD players, cellular phones, etc.

Classification of Integrated Circuits

Integrated circuits can be divided into two general classes, linear (analogue) and digital. Typical examples of linear integrated circuits are operational amplifiers whereas typical examples of digital integrated circuits are the logic gates and microprocessors that you met in the earlier chapters. It’s worth noting that a number of integrated circuit devices bridge the gap between the analogue and digital world. Such devices include analogue to digital converters (ADC), digital to analogue converters (DAC), and timers.

Digital integrated circuits can contain anything from one to millions of logic gates, flip-flops, multiplexers, and other circuits in a few square millimeters. The small size of these circuits allows high speed, low power dissipation, and reduced manufacturing cost compared with board-level integration. These digital ICs, typically microprocessors, DSPs, and micro controllers, work using binary mathematics to process "one" and "zero" signals.

Analog ICs, such as sensors, power management circuits, and operational amplifiers, work by processing continuous signals. They perform functions like amplification, active filtering, demodulation, and mixing. Analog ICs ease the burden on circuit designers by having expertly designed analog circuits available instead of designing a difficult analog circuit from scratch.

Pin Numbering for various IC packages

The pins are numbered anti-clockwise around the IC (chip) starting near the notch or dot. Often, but not always, GROUND and VCC are at opposite corners GROUND is usually on the lower left. VCC is usually on the upper right.