LSN 9 Electronic Hardware Design

Transcription

1 LSN 9 Electronic Hardware Design Department of Engineering Technology

2 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?

3 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

4 LSN 9 Design Analysis / Selection 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

5 LSN 9 Design Analysis / Selection QUALITY QUALITY COST ETHICS COST TIME TIME

6 LSN 9 Design Analysis / Selection 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

7 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

8 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 Technical Criteria 1 Technical Criteria 2... Technical Criteria 3 Ethical Criteria 1 Ethical Criteria 2... Ethical Criteria n Economic Criteria Totals Design 1 Design 2... Design n Weighted Weighted Score Score Score Score... Weighted Score

9 LSN 9 Electronic Hardware Design Passives and interconnect devices Input and output device consideration Power and power distribution Environmental Issues Digital logic devices

10 LSN 9 Passives & Interconnect Devices Connectors Headers Standard pin spacing of Test points IC sockets DIP PLCC PGA

11 LSN 9 Passives & Interconnect Devices Resistors Film Carbon or Metal Capacitors Film Foil or Metalized Ceramic Monolithic or Disk Electrolytic Aluminum or Tantalum

12 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 IOH max and IOL max (ECT224L Lab 2 & 3)

13 LSN 9 I/O Device Considerations 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 VIH min and IIH max 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

14 LSN 9 I/O Device Considerations 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 VIL max and IIL max is maintained for connected device while switch is open Pull-down resistors are typically much smaller than pull-up resistors given IIL max >>IIH max (must still be cautious of high power dissipation of resistor)

15 LSN 9 I/O Device Considerations 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

16 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

17 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

18 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

19 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

20 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

21 LSN 9 Digital Logic Devices Design concept Partition A B Design one block Design one block C Design interconnection between blocks Functional simulation of complete system Correct? Yes Physical mapping No D Timing simulation Correct? Yes Implementation No

22 LSN 9 Electronic Vendors Traditional electronic distributors Digikey (digikey.com) Newark (newark.com) Mouser Electronics ( Future Electronics ( Internet search Component locator Manufacturer datasheets

23 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 Ermer, G. A Normative Approach to Ethical Engineering Design, Proceedings of the 2002 CEEC Kleitz, W, Digital Electronics A Practical Approach, Prentice Hall, 7 th Ed., 2005