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Allegro Printed Circuit Board (PCB) Design Tutorial

The Allegro PCB Design Tutorial is intended for beginners in printed circuit board design who wish to complete a board using Cadence Allegro PCB Design Tool.

INTRODUCTION

Here is a general flow showing the steps required in the design of a PCB in Allegro.

1. From the schematics of the design you should have a list of allĀ  the components (resistors, capacitors, sockets, etc.) that you will be using on your board. Once you have the list, collect the datasheets and look at the suggested footprints (that is, the hole sizes or pads) in those documents. Many of the common footprints should already be in the library, but you may have to be generated.

In actual practice following are the main categories of the components used

Resistors, Capacitors,Inductors, Ferrite Beads
Diodes, Transistors, FETS, LEDs
Connectors, Headers
ICs, BGA ICs
Others

Interestingly, you will have to be most careful about the electrically simplest component – the connectors. You must get the physical part in hand to verify pin number 1 orientation and dimensions.

2. For each component, you have to create a footprint. Footprint is a physical view of the component that includes the holes through your board or pads for surface mount components. Footprints can be reused in the same board several times.

In practice, you will already have most of the footprint available and you should need to create only few additional footprints for a new design. You will need to be careful to verify that the existing footprint in your design library matches the mechanical dimension of the component according to its datasheet.

Many companies have the footprint available for their components as part of their component description and datasheet.

3. You have to create a schematic view of your board. This means adding different components on your board and connecting them with wires. We will be creating Schematics using Orcad. If you are not familiar with Orcad you may want to take an Orcad tutorial.

4. Once you have the schematic, you have to generate the netlist and import it to Allegro PCB Editor to complete the board layout. You place the components, define power and ground planes, route physical wires using this tool. Finally you must verify the board for errors.

5. Once you have the board layout, you generate a few files called artwork or gerber. The gerber files are used by PCB Manufacturer to manufacture the board.

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