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Using OrCAD Layout Plus

A Simple Guide

Written by Jose Cabral September 2006

Revised by Nithin Raghunathan

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SKETCH THE CIRCUIT YOU WISH TO LAYOUT

SKETCH THE LAYOUT

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COM J3

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COM

INPUT J2

COM

J1 OUTPUT

PIN 1 PIN 1

TWO EACH LM741

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1. Open Layout Plus. Start menu > Programs > ECE Software > Cadence PSD

15.1 > Layout Plus.

2. Select File > New. In the following popup, there are three things that must be

there in order to design a PCB. First is the Template, next is the Netlist, and the

destination to where you want to save the output .max file.

3. Click Browse next to the Input Layout TCH or TPL or MAX File. Select

_default.tch and click Open.

4. Click Browse next to the Input MNL Netlist File. Navigate to where you saved

your netlist file from the previous tutorial, highlight it and click Open.

5. Lastly select where you want to save the output .max file. This file will be among

the files sent to get the PCB made. You might put them in a separate folder.

Click Apply ECO when you have all the entries filled.

Changes to the schematic are done in Capture.

If you change the schematic design in Capture,

follow the procedure in the AutoECO section in

the Appendix to apply the changes in Layout.

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6. Next, you link a footprint to each component on your board. A footprint is the

layout of holes or pads that need to be on the PCB (so the part fits properly and

you can solder it on the PCB). Once you click Apply ECO, the Link Footprint to

Component popup will be displayed.

Click on “Link existing footprint to component…” In this case you are going to

be looking for a footprint to go with the resistor.

7. Now another popup will appear. This is where you will find the footprint for each

specific device. The device that you are currently linking to a footprint is listed on

the top of the window “Footprint for (device name)”.

8. The footprint for axial resistors is located in the TM_AXIAL library. The specific

footprint that will be used is the AX/RC07. A picture of the footprint will appear

in the window to the right. Click OK. The point to note is that RC05 is the

designation for 1/8 watt resistors will the RC07 is for ¼ watt resistors.

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9. The same popup (as described in step 6) will appear, only this time it will be for a

new part. Go through steps 6-8 for each part. The libraries and footprints for the

rest of the parts are as listed:

3 pin header: BCON100T library : BLKCON.100/VH/TM1SQ/W.100/3

2 pin header: BCON100T library : BLKCON.100/VH/TM1SQ/W.100/2

The numbers that are listed in the part name do have significance. For this part the

Number x Number is the Hole-to-hole length by diameter; last number is the Hole

Diameter. Each name for each library is define differently, refer to the OrCAD

Layout Footprint Libraries book for this information

10. Once you have linked all the parts to footprints an AutoECO report will popup.

Click Accept this ECO. Another popup will come up saying processing complete.

Click OK.

11. Now you will see a rubber-band version of your PCB layout. It is called a rubber-

band version because the yellow lines act as rubber bands connecting two pins

together. First deselect the Online DRC tool .

Another important point to note is that when the resistor is selected from the

Analog Library in Pspice while designing the schematic in Capture, the footprint

offered in Layout will be the RC05 footprint. This footprint AX/RC05 which is

smaller than the AX/RC07 footprint. This can be fixed by selecting the all the

resistors by dragging a select box around them and right clicking and selecting

properties and then footprint button in the properties dialog box. Then follow the

step 8 to select a new footprint.

Note also that the bypass capacitors are placed at one edge of the screen.

First perform Step 12.

Steps 13 and 14 will illustrate how to move the capacitors to the correct locations.

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12. Now, before you begin to lay down the traces, it is necessary define the board’s

outline. Click the Obstacle Tool . Draw an outline for your PCB (a simple

rectangle the size of the completed PCB). Before you finish your outline right

click and select properties.

In the following popup, you can define the obstacle name. Use “Board Outline”

to define this obstacle as the board outline. It needs to be on the Global Layer.

Click OK when done. To finish the Board Outline, right click again and select

End Command. Click OK when done.

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13. Now that the board’s outline defined, it is time to place the parts where you want

them. Select the . Now you can click and drag each component into the

board outline and place them where you want them. Continuing the example:

NOTE: To rotate the component just right click the component and select Rotate.

To change the placement and routing settings see Appendix I.

14. The parts are placed and now it’s time to run the traces that connect the parts.

Select the Add/Edit Route Mode Tool . Select the layer where want the trace.

The top layer is the top of the PCB board and all traces on this layer are green in

color; the Bottom layer is the bottom of the PCB and the traces on this layer are

usually red in color.

Now click on a rubber band (one of the yellow lines connecting two pins) and

start running your traces. Make sure that they DO NOT overlap on the same layer,

that would be a short. Here is an example of the board with all the traces run.

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A point to note is that the power rails are a bit thicker than the other traces in the

circuit. Check the Appendix on increasing the width of the rails.

15. In the picture below, a Via is added to the output trace. A via is a plated through

hole that connects traces on the top and bottom of the board. In the example

below, the output signal path uses a via to hop over the common and V- traces. As

you can see the output trace starts out as a green trace indicating it’s on the top

layer and thro the via continues as a red bottom layer trace after crossing the two

red bottom V- and Common traces .

16. To insert a via, just right click when you are running a trace and select Add Via.

You may position the via on the trace as you wish.

TIP: Keeping the design open in Capture while laying traces and moving

components in Layout, enables the user to identify the component being

moved.

The components or the traces that are selected in Layout will also be selected

simultaneously in the Capture schematic.

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17. Now that the board is laid out, it is time to run another check on it to make sure it

is ready to be produced. Again the computer can only check for so many things, it

is up to the designer to make sure everything is alright. To start the design rules

check, you must first figure out the limitations of production. Just because you

can draw a 1mil trace doesn’t mean you can make it (cheaply anyway). For

example go to the webpage for Advanced Circuits www.4PCB.com and look up

what their limitations of production are. Once you find these numbers you have

add them in to design rules check. To do this select Options > Global Spacing.

18. In the route spacing table, you will be able to specify the settings that Layout uses

to check your design.

The two main rows that you will be concerned with are the TOP and BOTTOM

layers. These layers are the ones where the traces are currently located. For

example, decreasing the Track to Track value will allow you to place traces closer

together. All of the values listed are in mils (1000th

of and inch, .001in).

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19. Next, run the Design Rules Check utility. Click Auto > Design Rules Check…

In the following popup you will be able to select which tests you want to run.

Select the tests shown in the figure below.

Click OK when you have all

the boxes checked. If any errors

come up they will be labeled on

your PCB layout and the rule

violation will be popup for you.

To check that the components are placed and routed fully:

ViewDatabase SpreadsheetsStatistics.

Look for % Placed and %Routed.

They should say 100%. If not check your design.

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20. To make the PCB easier to understand, effective labeling is essential.

To add labels to your components, text is silk screened onto the PCB.

Click the Text tool .

Right click on the workspace and select New.

The following popup is where you edit your text

string and select the layer. If you put text on TOP

or BOTTOM, you will be able to see it in Layout

but it will NOT be visible on your final PCB.

In order for it to be printed, you need to add it to

SSTOP or SSBOT (Silk Screen Top, Silk

Screen Bottom).

NOTE: When adding text to SSBOT remember

that in Layout you are looking from the top

of the PCB so the text on the SSBOT layer though

it looks normal to you will be backwards when

printed on the board .In order to fix this,

select the mirrored check box in the Text Edit

dialog box. Below is an example of some

labeling and adding text.

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21. Adding dimensions to your design is also useful in determining the size of the

PCB and is also required by some PCB manufacturers. The dimension can be

added by selecting TOOLDIMENSIONNEW. Then you click near one edge

of the board and drag to other edge. Repeat the Process for the next side.

Changes to the schematic are done in Capture.

If you change the schematic design in Capture,

follow the procedure in the AutoECO section in

the Appendix to apply the changes in Layout.

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22. Now it is time for Post Processing, this will create the files that will be sent out to

get your PCB made. Go to www.4PCB.com to find out what files they will need

to create your PCB and then:

Click Options > Post Process Settings. The Post Process table pops up, this lists

what layers will be processed. The ones you want selected are TOP, BOTTOM,

SMT, SMB, SST, SSB,FAB. To enable/disable a layer right click and select

Properties. Check or uncheck the box labeled Enable for Post Processing.

23. While still in the Post Process table, you can right click a layer and select Preview

and see what each layer will look like. You can also print the layer being

previewed. This is a good way to double check your work and have a tangible

copy of what you have accomplished thus far.

24. Now all you have to do is click Auto > Run Post Processor. The layers are now

files that will be used to create a PCB. The output files have been automatically

saved to your working directory (where ever your Layout file is).

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Appendix I

Changing Routing and Placement Settings:

Changing the routing and placement settings will let you have more control over your

work area to get more precise placement of components and routs. First select Options >

System Settings. The System Settings will appear.

The most useful options are: the Visible grid, this is the grid that is displayed on the

workspace; the Place grid this grid determines the grid detail when you place your parts;

the Routing grid determines the detail when you lay your traces; and the Via grid

determines the grid detail when you add vias. Under Workspace Settings you can define

the size of your current workspace. The numbers that are listed in the picture above are

the setting that were used through the tutorial.

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Changing Net Widths

1) First select Tool NetSelect from Spread Sheet.

2) Select Cancel in the Net Selection Criteria Dialog Box. In the spreadsheet select

the net that you would want to edit and then right click and select properties from

the popup menu.

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3) A dialog appears as shown below. Edit the Min Width( which is minimum width

of the trace ) Conn Width( Which is the standard trace width when the trace is

drawn and Max Width ( which is the maximum width of the trace that can be

drawn).

4) If a trace whose width need to be changed is already drawn before the above steps

are complete , you can change the width by selecting the Add/Edit Route Mode

Tool and moving the cursor over it and hitting the W key on the key board.

5) A dialog box pup op as follows. Select the option you need and change the width

by entering the value in the field.

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AutoECO (Engineering change order)

1) Sometimes it may be required to make changes to the original circuit in Capture.

This can be done easily using Auto ECO.

2) First make the changes to the circuit in Capture. Then, make the netlist as shown

in the Capture tutorial.

3) Open the old Layout file for the circuit. You will receive a dialog box as shown.

4) Click yes and then the AutoECO dialog box will open up as shown. Select Apply

ECO button to complete the design. Look at the AutoECO report dialog box that

appears to note the changes that have been done to your Layout file

The Drop down box under

Options will allow you to

specify what type of changes

are to made to your PCB

layout in accordance with the

changes made to the

schematic in Capture.

For Example: Selecting the

“AutoECO” option would add

all new components and nets

but will not change the

footprints or the names for the

existing components but it

will delete all unused

components and nets.

Selecting the “AutoECO Add

Override” option would add

new components and nets but

will not delete the existing

components and nets.

To find out what each

selection in the dropdown box

does, look at the bullet points

that appear beneath it

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OrCAD Help

Further Help in OrCAD can be developed using the help feature available in OrCAD.

This feature can be accessed in two ways by clicking on the HELP menu Layout

Help or by pressing the F1 key anytime in the main window.

Now you can use the Contents or Index and Search tabs in the sidebar to look for the

Help needed.

OrCAD Tutorial

For those interested in developing further skill in OrCAD can do so using the Tutorial

available in OrCAD.

The tutorial can be accessed as follows HELP menu Learning Layout

Select the version that you would like to use and then a learning Layout dialog Box

pops up . Select the Lesson Menu button, to bring up the lesson menu and then click

on the individual lesson to learn the different aspects of Layout.

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