Transcript PADS_Schematic_Tutorial

Designing Printed
Circuit Boards –
PADS Logic
Robust
Low
Power
VLSI
Yousef Shakhsheer
[email protected]
Robust Low Power VLSI Group
Revision 1.0
Revision History
Revision History Date
Reviser
1.0
Yousef Shakhsheer (yas5b)
4/30/12
Notes
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Overview
This 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.
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Schematics
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Outline
 Schematics
 Creating a library/components
 Create a schematic
 Exporting designs to netlists
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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)
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Open a new schematic
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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 reused and shared
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Creating a Library
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Creating a Library
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Creating a Library
Keep on pushing up until tutorial is on the top of the list
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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)
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Create a part
 Lets create a part
 SMT: LT1167 - Single
Resistor Gain
Programmable,
Precision
Instrumentation
Amplifier
 http://www.linear.co
m/product/LT1167
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Create a part
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Create a part
Add part information. See the pictures
for details.
Hit OK.
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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 autogenerate it for us
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Let’s draw a symbol
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Setting a Decal Name
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Lets draw the decal
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CAE Decal Wizard
A simple tool for quick creation of multi-pin symbols.
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Return to the part editor.
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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.
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Let’s add a part to our schematic!
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Add a LT1167 and a 1206 resistor
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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”
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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
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Example (this is not a functional
circuit)
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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
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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
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Export an Netlist for Layout
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On Netlist Export
Two files will open up.
1. Whatever you named your netlist.asc – The
netlist for your schematic
2. 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
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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
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Creating a Bill of Materials
 File -> Reports
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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
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You’re Done!
See the Layout tutorial for creation of an affiliated PCB design
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