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System ArchitecturesSystem Architectures
IntrductionIntrduction
Printed Circuit BoardsPrinted Circuit Boards
Evaluation BoardsEvaluation Boards
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IntroductionIntroduction
Defining the architecture is a critical issue
Several aspects need to be considered
Logical & functional issues
Hardware/software partitioning
Communication infrastructure
Mechanical issues
Support and assembly
Printed Circuit Boards (PCB)
Evaluation Boards (EVB)
System-on-Chip (SoC)
These choices strongly influence the design
Cost & development time
Constraints
Properties (security, safety, certifiability, ...)
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IntroductionIntroduction
Printed Circuit Board
A plastic insulating support to mount discrete components
Different support material depending on application scenarios
Several interconnection layers
Components mounted on both faces
Arbitrary shape
Can be “stacked”
Evaluation board
Ready-made, application specific platform
Integrates components for specific classes of applications
Provides customizable areas and large connectors
Variants
Industrial PC’s
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IntroductionIntroduction
System-on-Chip
A single silicon die integrates most of the functionalities
Can be full-custom, semi-custom or programmable
Limitation related to integrated technology
Capacitances, inductances, ...
Variants
Multi-Chip Modules
Stacked die
Network-on-chip approach
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Printed Circuit BoardPrinted Circuit Board
PCB integrate
Discrete components available on the market (COTS)
Custom components
ASIC, FPGA, PLD/CPLD
Programmable components
Microprocessors, Microcontrollers
Most of the system are realized on PCBs
Several important aspects to be considered
Components
Support
Mounting
Testing
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ComponentsComponents
First of all, select standard components
Passive components
Connectors, socket, dip-switch, pushbuttons, LEDs, ...
Resistors, capacitors, inductors
Active simple components
Transistors, Power transistors
Power supply
PCB need distributon and control of the power supplies
Different voltages, Different grounds
Often need
Sequencers
Voltage regulators
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ComponentsComponents
Filters
High-pass
Low-pass
Antialias
Converters
ADCs, DACs
Amplifiers
Input, output
Oscillators
Quartz, triggers, PLLs, DPLLs
Power stages
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ComponentsComponents
Electro-optical and magneto-optical
Interface between differen physical signal
Decouplers, phodiodes, infrared, laser
RF components
Antennas
Integrated and discrete
Amp-stages, modulation and demodulation
Display
7-segments leds
Alphanumeric and graphic LCD
Plasma, Organic displays
Touch-screens
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ComponentsComponents
Sensors
Very wide spectrum of components...
Analog devices that
Sense and measure a specific physical property
Encode this information with an electrical measure
Typical physical measures are
Temperature, pressure, acceleration, humidity, sound, light, EM-
field, orientation...
Digital components
Most of processing is performed digitally
Both as hardware devices and software programs
ASIC, FPGA, PLD, CPLD, programmable processors, ...
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PackagePackage
The same component exist with different packages
Tha package has a twofold goal
Protect the component
Make electrical contacs accessible from the outside
Packages differ with respect to
Mounting technology
Pin positioning and spacing
Coating material
The choiche of a specific package influences
System size, and thus PCB size and shape
Thermal and mechanical properties
EMC
Cost
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PackagePackage
Package influences mounting technology
Through-Hole
Pins enter and traverse the PCB surface and are soldered on the
opposite face
Surface Mounted
Pins are soldered on the surface of the PCB
Package defines pin positioning
In-Line
Pins lay on one or two sides of the packages (SIP, DIP, PDIP)
Small-Outline
Like In-Line, but smaller size and pitch (SOJ, SOP, TSOP)
Quad Surface Mount
Pins lay on all four sides of the package (CC, QFP)
Grid Array
Pins lay on the bottom surface of the package (PGA, BGA)
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PackagePackage
Package material can be
Plastic
Low cost, Poor theraml dissipation, Mechanically good
Ceramic
Higher cost, Very good thermal dissipation, Fragile
Rad-hard materials
Very hig cost, Resistant to EM radiation and cosmic particles
-- 1313 --
PackagePackage
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PackagePackage
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PackagePackage
Packages influence pin-counts and pitch
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PackagePackage
Packages influence efficiency
Ratio between die area and package area
Ranges from 5% to 60%
-- 1717 --
PackagePackage
Package influence PCB routing complexity
-- 1818 --
PackagePackage
Package influence thermal dissipation properties
Material
Pin cont & type
-- 1919 --
PackagePackage
Package influence thermal dissipation properties
Ambient temperature
-- 2020 --
PCBPCB
Imperial system is used instead of metric measures
Board size
Inch 1 in = 25.4 mm
Smaller dimensions (e.g. dielectric thikness)
Mil 1 mil = 0.001 in = 25.4 µm
Conducting material thickness
The weight of a fixed size sheet is used
Square foot 1 ft = 304.8 mm 1 sq.ft = 0.0929 m2
Ounce 1 oz = 28.349 g
E.g.: 2 oz thickness
Density is 2 oz/sq.ft, i.e. 619.29 g/m2
Density of metal copper at room temperature is 8.96 g/cm3
Conducting material thikness:
(619.29 g/m2)/(8.96 g/cm3) = 69.12 µm
-- 2121 --
PCB StructurePCB Structure
The PCB is made of several materials
Conducting material
Insulator
Glue
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PCB MaterialsPCB Materials
Conducting material
Mostly copper
Wiring
Power planes
Ground planes
Soldering pads
Thikness
From 0.5 oz to 3 oz
4-8 thiker layers
Power and ground
6-10 thinner layers
Interconnections
-- 2323 --
PCB MaterialsPCB Materials
Insulator
Insulates wires
Provides mechanical support
Fiber glass is very common
Fiberglass Epoxy Resin (FR-2 e FR-4)
Characteristics
Electrical
Permittivity and resistivity
Mecanichal
Resistant to stretching, compression, bending
Coefficient of thermal expansion
For special applications
Kevlar
Kapton, flexible supports
-- 2424 --
PCB MaterialsPCB Materials
Glue
Layers are stacked and glued
Glass resin pre-impregnated with epoxy resin (pre-preg)
At room temperature
Solid non-adhesive sheets
At suitable pressure and temperature
The viscosity decreases
Resins become adhesive
Maintain their insulating properties
Cooling and releasing pressure on the mounted PCB
Epoxy resing become solid
Assume the thermal, chemical and electrical properties requied for
the final manufact
-- 2525 --
PCB FabricationPCB Fabrication
Fabrication requires different phases
Preparation of dielectric supports
Dieletcric material impregnated with epoxy resins
Copper is used from sheets or by electrolytic deposition
Fabrication of wiring
Deposition of photoresist that polimerizes where exposed to light
Chemical etching of the unwanted copper
Layer assembly
Layers are stacked and interleaved with pre-preg
Pressed at a suitable temperature
Drilling
Mechanical or laser
The inner part of the holes is coated with copper
-- 2626 --
PCB FabricationPCB Fabrication
External layer fabrication
By photolitography and galvanostegy
The outer surfaces of the PCB are coated with a thiker copper
layer
Finishing
Mechanical polishing
Deposition of an insulating film, except in contact aread (pads)
-- 2727 --
PCB TestPCB Test
Electrical testing
Verifies if contacts are connected or insulated, as required
Measures the resistance between couples of points
Three types of testing equipmentBed-of-Nails
Flying-Probes
X-Ray
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PCB TestPCB Test
Bed-of-Nails
Up to 5000-10000 metal probes
Injects current in predefined
points in the circuit
Senses the current in other points
Programmable
-- 2929 --
PCB TestPCB Test
Flying-Probe
Few metal probes
Usually 4 to 8
Mechanical structure for precise
positioning of the probes
Measure the resistance between
couples of points
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PCB TestPCB Test
In special situation testing requires X-ray photograpy
Accurate inspection of buried connections
Testing after mounting components can be hard
Hidden contact points
X-ray images are checked
Manually, by experienced designers
Automatically, by means of image recognition tools
-- 3131 --
MountingMounting
Positions and solders components on the PCB
Manual
For small PCBs and limited volumes, typically prototypes
Automated
For large PCBs and/or volumes
Mandatory for critical components (high pin count, small pitch)
Main problems
Components must be poitioned with extreme accuracy
Soldering
SIP, DIP, ... Manual soldering feasible
QFP, PGA, BGA, ... Manual soldering unfeasible
Automatic mounting requires two phases
Components positioning
Pin soldering
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Mounting Mounting –– Positioning Positioning
Realized with machines called “pick & place”
Programmable
Very complex and expensive
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Mounting Mounting –– Positioning Positioning
Such machines have a variable
number of feeders
Lodgings for strips of components
Feeders prepare components
in such a way that a moving
mechanical arm can
Pick the components
Position components on the PCB
These actions are programmaed
High-machines
200 feeders
2 moving arms/heads
Optical vision for positioning
~ 30.000 comp/hr (~9 comp/s)
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Mounting Mounting –– SolderingSoldering
Components on the PCB are not soldered yet
Must be fixed before soldering
Mechanical fixing
Pint are forced into PCB holes
Adhesive fixing
With epoxy resins
Then, two soldering techniques
Reflow soldering
Contacts are pre-covered with a soldering paste
The PCB is heated and then cooled to complete soldering
Wave soldering
Liquid solder is deposed directly on contact points
The PCB is heated and then cooled to complete soldering
-- 3535 --
Evaluation BoardEvaluation Board
Evaluation board, also called, Demo boards
Are redy-made PCB integrating a full system
Can be designed for devepment of different types of systems
Microcontroller based
Digital signal processor based
FPGA/CPLD based
More complx systems
Are customized for different applications
Numeric and digital signal processing
Networking
Image and video processing
…
Often used for
Prototyping of a system and application
Reference design for custom system
-- 3636 --
EVB Example: EVB Example: XilinxXilinx CPLDCPLD
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XilinxXilinx CPLD: 7CPLD: 7--segment displaysegment display
Digits are time-multiplexed
When the anode is low the 7+1 cathode signal control the
segments of the display
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XilinxXilinx CPLD: 7CPLD: 7--segment displaysegment display
Encoding
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XilinxXilinx CPLD: 7CPLD: 7--segment displaysegment display
Timing for digit time-multiplexing
Refresh period: 1ms – 16ms
Anode low period: 240us – 4ms
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XilinxXilinx CPLD: Sample CPLD: Sample topleveltoplevel designdesign
BCDC0
counter
CKPRE
prescaler
DCTRL
displayctrl
BCDC1
counter
001
0000
1
0000
clk
reset
ce
step(2:0)
ss(0:7)
an(3:0)
main
-- 4141 --
XilinxXilinx CPLD: CPLD: PinoutPinout
50 MHz clock
Signal: clk
PIN: 77
Spartan 2
Device: xc2s50
Speed grade: -6
Package: pq208
7-segment display
Anodes PINs:
75,71,69,60
Cathode PINs:
74,70,67,62,61,
73,68,63
Step programming switches
Signal: step(2:0)
PINs: 81,82,83
Reset
Signal: reset
PIN:59
Count enable
Signal: ce
PIN:58
Power supply
JTAG Port
-- 4242 --
EVB Example: TI RFIDEVB Example: TI RFID
-- 4343 --
TI RFID: FeaturesTI RFID: Features
USART for I/O Communication
Three General Purpose I/O lines
Dual Frequency Operation
134.4KHz
13.56 MHz
Multi-Protocol
TI RFid LF Products
TI RFid HF Tag-It
ISO 15693
ISO 14443 A/B
Custom Firmware Downloadable
Scalability/Modular Architecture
Power On-Reset Operation
Firmware Upgradable
-- 4444 --
TI RFID: ConnectorsTI RFID: Connectors
-- 4545 --
TI RFID: Mechanical propertiesTI RFID: Mechanical properties
-- 4646 --
EVB Example: TMS320VC5505 DSPEVB Example: TMS320VC5505 DSP
-- 4747 --
TMS320VC5505 DSP: FeaturesTMS320VC5505 DSP: Features
TMS320C5504 or TMS320C5505 fixed point low power DSP
Devices
TLV320AIC3254 32-bit programmable stereo codec
OLED color LCD display (128x128 pixels)
Interfaces
Stereo line in, headphone out, microphone in
I2C, SPI, USB 2.0
MMC/SD slot, CE-ATA connector, RS232 interface
Connectors
10 user defined push button switches
Analog front end connectors
Two expansion connectors for memory cards
Other
External oscillator socket, Battery Holder, +5V power supply
-- 4848 --
TMS320VC5505 DSP: SoftwareTMS320VC5505 DSP: Software
A complete Integrated Development Environment (IDE),
Efficient optimizing C/C++ compiler
Assembler
Linker
Debugger
Profiler
Project manager
DSP/BIOS real-time kernel
Chip Support Library
Board Test Package
-- 4949 --
EVB Example: MC9S12DP512 EVB Example: MC9S12DP512
-- 5050 --
MC9S12DP512: SchematicsMC9S12DP512: Schematics
-- 5151 --
Further readingFurther reading
1. Packaging
e-book chapther
2. The evolution of microprocessor packaging,
Intel
3. Using BGA Packages,
Fairchild Semiconductor, Application Note
4. Thermal Considerations for Surface Mount Packages,
Fairchild Semiconductor, Application Note
5. IC Package Thermal Metrics
Texas instruments, Application Note
6. S4100 Multi-Function Reader Module,
Texas Instruments, Data Sheet
7. Examples of package data sheets
Analog Devices
