LSN 9 Electronic Hardware Design - University of Daytonacademic.udayton.edu/scottschneider/courses/ECT224/Course Notes... · LSN 9 –Electronic Hardware Design ... –Ceramic •Monolithic

Department of

Engineering Technology

LSN 9

Electronic Hardware Design

ECT 224 Digital Computer Fundamentals

ECT 224 Digital Computer [email protected]

LSN 9 – Engineering Design Process

• Define the problem / requirements

– Define the target values

• Develop solutions

– Research existing technologies and methods that could

be adapted to the design

• Evaluate the solutions

– Select the one that best meets the requirements

• Verification of selected solution

– Simulation / prototyping / unit and system testing

• Modifications and improvements of design

?


LSN 9 – Design Analysis / Selection

“ Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire world, and all there ever will be to know and understand. ”

– Albert Einstein

“ There comes a time in the history of any project when it becomes necessary to shoot the engineers and begin production ”

– Unknown



• All design challenges are ambiguous unlike answers to

mathematical expressions

• There are always several “correct” answers to any

design challenge

• Not all design solutions are equally good, however,

some are definitely wrong

• All designs could be improved if there was more time

and resources



COST TIME

QUALITYQUALITY

COST

TIME

ETHICS



• All engineering professional societies have a code of ethics– IEEE

• To accept responsibility in making decisions consistent with the safety, health and welfare of the public, and to disclose promptly factors that might endanger the public or the environment

• To avoid real or perceived conflicts of interest whenever possible, and to disclose them to affected parties when they do exist

• To be honest and realistic in stating claims or estimates based on available data

• To reject bribery in all its forms

• To improve the understanding of technology, its appropriate application, and potential consequences

• To maintain and improve our technical competence and to undertake technological tasks for others only if qualified by training or experience, or after full disclosure of pertinent limitations

• To seek, accept, and offer honest criticism of technical work, to acknowledge and correct errors, and to credit properly the contributions of others

• To treat fairly all persons regardless of such factors as race, religion, gender, disability, age, or national origin

• To avoid injuring others, their property, reputation, or employment by false or malicious action

• To assist colleagues and co-workers in their professional development and to support them in following this code of ethics


LSN 9 – Utilizing Design Norms

• Design norms are moral guidelines that can be used to

determine ethical behavior

– Normative design balances tradeoffs between technical,

economic, schedule, and ethical constraints

• Common engineering design norms

– Cultural appropriateness

– Transparency

– Stewardship

– Harmony

– Justice


LSN 9 – Utilizing Design Norms

• Design decision matrix

– Allows engineers to quantify and objectify a decision

between multiple alternative solutions to a particular

problem

Criteria Weights Score

Weighted

Score Score

Weighted

Score Score

Weighted

Score

Technical Criteria 1


. . .


Ethical Criteria 1

Ethical Criteria 2

. . .

Ethical Criteria n

Economic Criteria

Totals

. . .

Design 1 Design 2 . . . Design n


LSN 9 – Electronic Hardware Design

• Passives and interconnect devices

• Input and output device consideration

• Power and power distribution

• Environmental Issues

• Digital logic devices


LSN 9 – Passives & Interconnect Devices

• Connectors

– Headers

• Standard pin spacing of 0.100”

– Test points

– IC sockets

• DIP

• PLCC

• PGA


LSN 9 – Passives & Interconnect Devices

• Resistors

– Film

• Carbon or Metal

• Capacitors

– Film

• Foil or Metalized

– Ceramic

• Monolithic or Disk

– Electrolytic

• Aluminum or Tantalum


LSN 9 – I/O Device Considerations

• Light Emitting Diodes (LEDs)

– Typically drop ~1.7V when forward biased

– Illuminate at ~5 to 20mA

• Traditionally driven by digital logic devices in a “sinking” layout

• Require current limiting resistors that account for IOHmax and IOLmax

(ECT224L Lab 2 & 3)



• Sizing pull-up resistors for switches to GND

– Pull-up resistors are used to keep a terminal at a logic 1

instead of floating when the switch is open• Must select resistor such that VIHmin and IIHmax

is maintained for connected device while switch

is open

• Must select resistor large enough not to draw

excessive current and lead to high power

consumption when switch is closed

• 10kΩ resistors are typical



• Sizing pull-down resistors for switches to Vcc

– Pull-down resistors are used to keep a terminal at a logic 0

instead of floating when switch is open• Must select resistor such that VILmax and IILmax

is maintained for connected device while switch

is open

• Pull-down resistors are typically much smaller

than pull-up resistors given IILmax >>IIHmax (must

still be cautious of high power dissipation of

resistor)



• Switch bounce

– Occurs during switch opening and closing due to a springing

action of the mechanical contacts (ECT224L Lab 7)

– All mechanically switched inputs must be debounced


LSN 9 – Power and Power Distribution

• Decoupling capacitors

– Capacitors that are placed between Vcc and GND

– Act as sources of current during peak demand periods

• At peak demand, power supplies are too slow and far away to supply

the necessary current

– Xilinx recommends 0.01 F to 0.1 F local decoupling

capacitance for each Vcc pin (keep the power close)

• Use capacitors with low series impedance (ceramic caps)

• Use one tantalum capacitor of 10 F to 100 F between Vcc source

and GND to back up the local caps


LSN 9 – Power and Power Distribution

• Require means of providing appropriate DC voltage

values

– AC / DC conversion required for AC outlet powered device

• Linear vs. switching conversion

• Wall transformers (wall-warts) vs. integrated

– DC voltage regulation required for DC powered devices

(batteries) and to obtain final regulated DC voltage value(s)

• Linear vs. switching regulation

• BE CAREFUL DC values of digital logic devices vary

– TTL / CMOS voltage levels

– PLD core / IO voltages


LSN 9 – Environmental Issues

• Restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS)

– Originated in the EU and became law there on 7/1/06

– Restrictions of :

• Lead (Pb), Mercury (Hg), Cadmium (Cd), Hexavalent Chromium (CrVI), Polybrominated Biphenyls (PBB), and Polybrominated Diphenyl Ethers (PBDE)

– Other regulatory actions on waste from electronic fabrications (green initiatives)

• The China RPCEP (Regulation for Pollution Control of Electronic Products) goes into effect July 1, 2006

• The Japan JGPSSI (Japan Green Procurement Survey Standardization Initiative) goes into effect July 1, 2006

• The California SB20 (Electronic Waste Recycling Act of 2003) goes into effect January 1, 2007

• Australia, Canada, Korea, and Taiwan are adopting the EU RoHS directive


LSN 9 – Environmental Issues

• Recycling of electronic devices

– Waste Electrical and Electronic Equipment Directive

(WEEE)

– In the United States, 70% of all toxic waste comes from

discarded electronics

– Increase lifespan through planned upgradability in device

design

– Device design should promote the easy removal of

dissimilar materials


LSN 9 – Digital Logic Devices

• Digital logic hardware integration issues

– Current limitations for I/O (ECT224L Lab 3)

– Clocking sources (ECT224L Lab 8)

• PLD specific integration issues

– Device selection

• Capacity

• OTP / reprogrammable

– Programming interface

• JTAG

– Pin selection for I/O and clock signals

– Package type


LSN 9 – Digital Logic Devices

Design interconnection between blocks

Functional simulation of complete system

Correct?

Physical mapping

Timing simulation

Correct?

Implementation

No

Yes

No

Yes

Design one block Design one block

Partition

Design conceptA

B

C

D


LSN 9 – Electronic Vendors

• Traditional electronic distributors

– Digikey (digikey.com)

– Newark (newark.com)

– Mouser Electronics (www.mouser.com)

– Future Electronics (www.futureelectronics.com)

• Internet search

– Component locator

– Manufacturer datasheets

http://www.futureelectronics.com/


LSN 9 – Homework

• Reading

– Technical articles specific to electronic hardware design with PLDs

• Bulletproof CPLD design practices.pdf

• Driving LEDs with cplds.pdf

• Power Distribution Systems Design Using Decoupling Capacitors.pdf

• FPGA Journal Green Electronic Design.pdf

• References– http://www.micron.com/students/engineer/design.html

– Ermer, G. A Normative Approach to Ethical Engineering Design, Proceedings of the 2002 CEEC

– Kleitz, W, Digital Electronics – A Practical Approach, Prentice Hall, 7th Ed., 2005

Student References/Bulletproof CPLD design practices.pdf

Student References/Driving LEDs with cplds.pdf

Student References/Power Distribution Systems Design Using Decoupling Capacitors.pdf

Student References/FPGA Journal green_engineering_design.pdf

http://www.micron.com/students/engineer/design.html

Documents

LSN 9 Electronic Hardware Design - University of Daytonacademic.udayton.edu/scottschneider/courses/ECT224/Course Notes... · LSN 9 –Electronic Hardware Design ... –Ceramic •Monolithic