Designing Printed Circuit Boards – PADS Logic

RobustLowPowerVLSI

RobustLowPowerVLSI

Designing Printed Circuit Boards –PADS Logic

Yousef Shakhsheeryousefshak@gmail.com

Robust Low Power VLSI GroupRevision 1.0

RobustLowPowerVLSI

2

Revision HistoryRevision History Date Reviser Notes

1.0 4/30/12 Yousef Shakhsheer (yas5b)

RobustLowPowerVLSI

3

OverviewThis tutorial is intended to get people started with the PADS flow and basic PCB schematic capture.

We use PADS Logic 9.3.1 for schematics and PADS Layout 9.3.1 for PCB layout for this tutorial.

RobustLowPowerVLSI

4

Schematics

RobustLowPowerVLSI

5

Outline Schematics

Creating a library/components Create a schematic Exporting designs to netlists

RobustLowPowerVLSI

6

Schematics The schematic is a top-level symbolic

representation of the circuit you are designing It affiliates parts (symbols in the schematic)

with nets (connections in the schematic)

RobustLowPowerVLSI

7

Open a new schematic

RobustLowPowerVLSI

8

Libraries Libraries hold sets of parts (symbols and PCB

decal information) Libraries are not affiliated with a particular

schematic or design so that parts can be re-used and shared

RobustLowPowerVLSI

9

Creating a Library

RobustLowPowerVLSI

10

Creating a Library

RobustLowPowerVLSI

11

Creating a Library

Keep on pushing up until tutorial is on the top of the list

RobustLowPowerVLSI

12

Parts Parts reside in libraries, they contain all the

information required to place a component onto a PCB

Affiliate schematic symbols with a PCB footprint (see Layout tutorial for more)

RobustLowPowerVLSI

13

Create a part Lets create a part SMT: LT1167 - Single

Resistor Gain Programmable, Precision Instrumentation Amplifier

http://www.linear.com/product/LT1167

RobustLowPowerVLSI

14

Create a part

RobustLowPowerVLSI

15

Create a part

Add part information. See the picturesfor details. Hit OK.

RobustLowPowerVLSI

16

Symbol Symbols are what show up when we add a part

to a schematic We can either create this symbol by-hand (from

a set of pins and lines) or use a wizard to auto-generate it for us

RobustLowPowerVLSI

17

Let’s draw a symbol

RobustLowPowerVLSI

18

Setting a Decal Name

RobustLowPowerVLSI

19

Lets draw the decal

RobustLowPowerVLSI

20

CAE Decal WizardA simple tool for quick creation of multi-pin symbols.

RobustLowPowerVLSI

21

Return to the part editor.

RobustLowPowerVLSI

22

Back to the schematic File→Exit Parts Editor

You will get two warnings. You can ignore them for the time being

Warning: Duplicate pin name RG for pin number 8 on Gate A.Warning: Part has no PCB Decal assigned.

RobustLowPowerVLSI

23

Let’s add a part to our schematic!

RobustLowPowerVLSI

24

Add a LT1167 and a 1206 resistor

RobustLowPowerVLSI

25

Schematic Basics F2 to create wires Two types of connections

Physical wire connection Off page connectors: click on the wire and then right click, “Add off

page connectors”

Additional you can use the ground symbol by click on the first part of the wire and then right clicking and selecting “Ground”

RobustLowPowerVLSI

26

Lets put together an example schematic

Part numbers: U1- LTC1167 U2- LDO – Digikey P/N - LP3996SD-3333CT-ND U3- MicroUSB – Digikey P/N - A31727CT-ND P1- Power Jack – Digikey P/N - CP-037A-ND

RobustLowPowerVLSI

27

Example (this is not a functional circuit)

RobustLowPowerVLSI

28

Other schematic entry tips Right click on the

schematic for the selection menu

You can make it so you can only click on/select only certain objects

Always change the background color before exporting/printing any schematics from PADs layout

RobustLowPowerVLSI

29

Netlists The netlist affiliates a group of symbolic pins

with a what is referred to as a “net” We sometimes label these nets for convenience

(Vcc and GND are common names) but we do not have to name all the nets

When the netlist is exported all non-named nets have their names auto-generated so the layout tool can correctly affiliate all the pins

RobustLowPowerVLSI

30

Export an Netlist for Layout

RobustLowPowerVLSI

31

On Netlist ExportTwo files will open up. 1. Whatever you named your netlist.asc – The

netlist for your schematic2. tutorial.err – An error report file (make sure

you always check this)At this stage:1. You haven’t assigned PCB decals, so you should see errors for this 2. You may also see single ended nodes

RobustLowPowerVLSI

32

Bill of Materials Once we have created a PCB we will need to order

all the components necessary to populate the board The Bill of Materials (BoM) makes this easy and

outputs a simple list of items in the schematic Any field included in the attributes of a part included

in a schematic is allowed to be added to the BoM for that schematic, this means we can have columns like DigiKey Part Number, Approximate Cost, or even product page URL if these attributes are added to the parts on creation

RobustLowPowerVLSI

33

Creating a Bill of Materials File -> Reports

RobustLowPowerVLSI

34

BoM Export The BoM is a text-based report but a CSV

output file can be created (this allows an effected export to Excel)

The BoM is a useful tool both for ordering parts and also for population as it affiliates part numbers with part reference numbers in the schematic and layout

RobustLowPowerVLSI

35

See the Layout tutorial for creation of an affiliated PCB design

You’re Done!