Advertisement

Blog

Strategies for Components Documentation

When a manufacturer offers a product for sale, the design engineers expect to have access to documentation that provides sufficient information to determine whether the product will perform as needed for the design under consideration. This is a fundamental requirement for electronic component parts and assemblies.

For components that are intended for use in assemblies, the manufacturer will not only furnish a datasheet covering the essential parameters of the part, but may also include an “Application Note” directly within the datasheet. This is usually in the form of a practical clarification of some aspect of the component, coupled with small block diagrams or schematics.

However, for more sophisticated parts, the Application Notes may exist as separate and more comprehensive documents. For a typical semiconductor datasheet, {complink 5703|Texas Instruments Inc.} has published a paper titled “How to Read Datasheets” by C.J. Ganier. The paper is fairly comprehensive; if you would like to become more familiar with datasheet terminology, this is an excellent introduction. Here is the intro of the Abstract:

    For every electronic component or series of components, the manufacturer or designer produces a datasheet. In its early stages, a datasheet might be the specifications the designer works from; but, by the time the device is released, the datasheet is the essential piece of information that describes exactly what the component does. Everything from the smallest resistor to the most elaborate processor needs a datasheet.

    Datasheets focus on electrical properties and the pin functions of the device; usually the inner workings of the device are not discussed. This is partly to make industrial espionage more difficult, and also because the user should not need to know the internal workings of the device. In practice, if you find that you need to know how a particular product works internally, you can often call the manufacturer and find what you need to know.

For most documentation, the following is covered in great detail:

  • Manufacturer's part numbers and associated options specific to unique characteristic variations of the part. These are usually found in a section labeled “Ordering Information.” The main part number is usually at the top of the first page in a large, bold text.
  • The part description
  • A picture or line drawing of the part
  • The introductory general feature information
  • The package or form with dimensions
  • Pin-out diagrams
  • Tables for function and operating characteristics (usually specified as “Min,” “Typ,” or “Max”). Values, including, but not limited to:
    1. Temperature
    2. Voltage
    3. Power
    4. Power dissipation
    5. Current
    6. Impedance
    7. Frequency
    8. Timing
    9. Value
    10. Tolerance
    11. Package — form factor options with part number ordering information
    12. Package thermal characteristics
    13. Gain (for transistors)
    14. Switching speed
    15. Humidity or other Environmental limits
  • Additional drawings showing footprints, land patterns, or hole cutout specifications
  • Materials used to make the part if required by law
  • Charts showing various performance characteristics on a two-axis plot format

Component documentation should be quickly accessible via a part management system that is either 1) based upon a software database application that links “attachments” to part numbers; and/or 2) a hard-copy set of files storing all relevant documentation associated with the component or assembly part number. Refer to the core-disciplines tab at www.componentsengineering.com/core-discplines for more detailed information on this and related engineering subjects.

It is of the utmost importance to refer to the manufacturer's datasheets when qualifying a part to determine if the part performs as stated. Having the datasheet will also help with designing the qualifying test procedure unique to the component or component family type. Recently, Silicon Expert released a Web-based search engine that has datasheet information on more than 180 million parts. This engine can be found at www.datasheets.com or at other various (hosting) Websites, including www.ebnonline.com and www.componentsengineering.com. Datasheets.com also has inventory counts and costs at the various participating distributors. It is an excellent source for part availability searches in general.

Purchasing must also have access to the component data information but may not require the full set of datasheets. This is why the component engineer creates a Purchasing Specification Document (PSD) or a Specification Control Drawing/Document (SCD). This is an abbreviated form of the full specification citing the critical parameters of the part and usually incorporating a drawing of the part with dimensions, if applicable.

Many times, a vendor will take advantage of a purchasing agent's emergency part purchase requirement and suggest an alternate part that is not a true parametric substitute. The purchasing agent is bound to the PSD and is not allowed to purchase a substitute part that is not on the PSD or SCD. The purchasing agent may send non-proprietary PSDs to a vendor to help the vendor better match the original component, but the component can only be purchased after it has been added to the Part Master's approved vendors list by the component engineer or when a sustaining or design engineer has signed off on a temporary manufacturing deviation, thereby allowing the use of the substitute part only until the original manufacturer’s part number can be sourced.

This is the best way to avoid production problems due to underperforming or non-performing part substitutions. PSDs and SCDs must also be under revision control. A PSD form template is downloadable here.

Having all the datasheets available either in hard copy or in PDF soft copy with links is the best practice for rapid retrieval of critical part information. These datasheet files should be part of the overall project file created for the product during the R&D phase.

32 comments on “Strategies for Components Documentation

  1. Barbara Jorgensen
    December 19, 2011

    Douglas–great, detailed information. One question: in your experience, how often should one worry about updating their component database? I know that information gets stale even on on the Web, so it must come up… 

  2. stochastic excursion
    December 19, 2011

    The components engineering website is a great resource.  Data sheets available directly from an ERP system's part master would be very convenient to have.  I wonder how document control specialists could facilitate this.

  3. Nemos
    December 19, 2011

    Very Helpful article , I want also to mention how much help you have when you are working in the Service sector and you can have freely access to all of these documentations and part manuals. But problem occurs when the part is not in the market any more and you are trying to find a replacement for that. I dont Know how but we must find a solution to that ….

  4. dalexander
    December 19, 2011

    Barbara, Fortunately, there are component “alert” services to which a company can subscribe. The nature of these alerts deal with different Part Master maintenance concerns. Of major concern are the EOL, End Of Life alerts. However, many general form, fit, or function changes are captured in PCN, Product Change Notices, issued by the manufacturer. The absolute best way to keep a part's data up-to-date is to have a service that references the company's internal part numbers to targeted alert notifications that “pushes” the part particulars to the service subscriber's email automatically. So, if a company had their entire Item Master Part listing automatically assigned to an alert service as mentioned, then the manual scrub no longer becomes necessary. Soon to be arriving in January is one such service offered by EEContent.com which will not only cross reference a company's internal part numbers to PCN And EOL type alerts, but also environmental compliance such as REACH, Registration-Evaluation-Analysis-restriction of CHemicals. These chemicals being further defined as SVHC or Substances of Very High Concern. The EEContent.com service will perpetually scrub any BOM uploaded to the service so that every REACH, EOL, and PCN alert is tracked against every internal part number. This will not only save the company a lot of effort in keeping the part's list current, but will also provide instantaneous analysis of the company's products readiness to ship to REACH compliant countries. The other reason a part database would be periodically scrubbed would be because companies are always buying up other companies and obsoleting/obscuring the original manufacturer's name and part number. Hence it is best to have the ability to track a manufacturer's genealogy as well. Parts listed under Motorola several years ago, may now be manufactured by Freescale. A notice service offering genealogy information is most helpful for keeping the AVL part of the Item Master up-to-date. EEContent.com also has the genealogy service available as part of their standard subscription service. Barbara, I appreciate your manufacturing savvy a lot. I believe there is much that readers can gain from reading blog responses and not just the content of the blogs themselves. My recommendation, in answer to your question, ” how often should one worry about updating the component database” is a lot less than they do without a subscription service. EEContent is the most affordable service available now and this is the team that introduced PCN Alert back in the late 90s early 2000s. So now with the advances in the Internet and lower cost of storage and services, in my opinion, every company should be actively pursuing any alert service that gives them the most comprehensive alert types, while not straining the company's fiscal constraints.

  5. dalexander
    December 19, 2011

    Memos. Try http://www.lansdale.com for obsolete parts replacements. These guys bought up the old dies and masks and still manufacturer many parts that were obsoleted by the original manufacturer. As a global pioneer in IC products life cycle management, Lansdale manufactures over 3,000 classic design ICs in the original package, exactly as they were created and produced by AMD, Fairchild, Freescale Semiconductor, Harris, Intel, Motorola, National, Philips (formerly Signetics), and Raytheon. If you need help with specific replacements, just email me or visit http://www.componentsengineering.com and sign up. No charge for helping so let us know what tough part you are attempting to replace now.

  6. mario8a
    December 19, 2011

    Tthis article is very helpfull and outlines the best practices to get appropiate datasheets, in development those documents are live and changing all the time based on customer expectations

  7. SunitaT
    December 20, 2011

    @Douglas, Once again great article. Very informative. To be frank datasheets always scared me. I will definitely refer “How to Read Datasheets” by C.J. Ganier so that I can overcome this fear.

  8. Nemos
    December 20, 2011

    Thank you a lot Alexander, I will check the site .

  9. prabhakar_deosthali
    December 20, 2011

    Having the complete technical documentation of the components used in a product design always helps in testing and servicing of the products in the field.

     

    I would like to mention one important point here. Not all the specifications of a given part may be applicable in the design consideration of a part and there may be some leverage available in certain specifications. If the designer documents -what was required specification in his design against what was the  specification of the chosen component – it will help finding second source components which may not be matching the original part in terms of specifications but will be able to meet the designers specifications.

  10. mfbertozzi
    December 20, 2011

    I've taken a look at both interesting editorial and great posts; I am wondering if similar guidelines could be applied in dual mode, for software.

  11. Houngbo_Hospice
    December 20, 2011

    Some of the components documentation principles can also be applied to software documentation. However, it is difficult to have everything documented because of deadline constraints. Developers sometimes just want to have their jobs done and never have enough time to spend on providing support for their software.

  12. Houngbo_Hospice
    December 20, 2011

    @prabhakar_deosthali 

    “Not all the specifications of a given part may be applicable in the design consideration”

    Agreed, but it is better to have the documentation to serve for guidelines. This way, you can use the information to search for similar components when you cannot find the component with the actual (same) specs.

  13. dalexander
    December 20, 2011

    Prabhakar and Hospice, Your comment on critical parameters is key for selecting emergency replacements to keep a line running, but the substitute part must be given a new internal part number and a TMD, Temporary Manufacturing Deviation must be issued and authorized to avoid the possibility of using the part in an older release where the non- critical parameter in the substitutable application may be critical in the older design. I have seen this happen when Design Engineers are using the same part in very different circuits. Whenever two or more parts have any form, fit, or function variances, then each should receive their own internal part numbers to avoid any application conflicts in past, present, or future designs. Thank you for commenting on this as it brings to everyone's attention this very important consideration.

  14. Barbara Jorgensen
    December 20, 2011

    Douglas–thanks for the detailed and thoughtful reply. (I know just enough to make me dangerous…) Seriously, I hear a lot about out of date content and it drives people crazy.

  15. Brian775137
    December 20, 2011

    Barbara:

     As always, Douglas has written a great article.  Parts need to be tightly controlled in order to negate having problems.

    Without tight control of all of the parameters of each part via a PSD or SCD, there is aways the possibility of a part ALMOST (but not quite) performing as needed.  By not performing as required for some critical parameter, the desired function may be compromised.  How much it is compromised or “degraded” from what is needed, determines if the substitution will work or not.  Often this is not found out until after the substitute part is used and released to the end user.  Then, if the degradation is too much, it'll come back to you and “bite” you severely. (No-one likes to be bitten, expecially if money and customer satisfaction is involved)

    Tight control of the part and updating the AVL for each part change, is mandatory for having far less problems, saving money and maintaining customer satisfaction.

    Remember, the ultimate choice of what part is to be used is up to the Design Engineer/Component Engineer team.  Another item which is determined by the DE/CE team along with the program contract, is the Reliability of the part. (We will be addressing the RELIABILITY of parts in further articles)  Neither of these can be changed by the Purchasing person within the company.  Purchasing's function is to obtain the exact desired part at the lowest possible price, with all of its associated parametric specifications and reliability considerations.

  16. Brian775137
    December 20, 2011

    Douglas:

    This is particularly true if you have a part which has one or more Reliabiity levels being used for different contracts within the same company.  The only safe ay to accomplish this is to have a separate Preferred Parts List (PPL) for each contract with the reliability level of the part being one of the part parameters specified.  I realize that this occurs mostly within the Aerospace community. but this only further supports the tight control needed for each part being used so that the exact part (as determined by the DE and the CE AND the end product customer's requirements) is used appropriately.

  17. Brian775137
    December 20, 2011

    Prabhakar:

    It is agreed that the same considerations should be used for software, but that is the function of the IT person involved, and usually is not something that is considered by a DE or a CE.

  18. dalexander
    December 20, 2011

    Brian,

    I think it may be time to write an article on the PPL (Perferred Parts List) and the selection criteria for identifying the candidates for the list. Because this list is a subset of the Item Master, the component selection guidelines are adhered to in practice, but there is a super selection process that brings a component to PPL status. Look for this in the next article for the Best Practices series.

  19. mfbertozzi
    December 21, 2011

    I've very appreciated the article and clear schema used for summarizing guidelines for composing professional docs. In the electronic world, we could say english as preferred languages is a must, but I am wondering how could be solved issues on translation while we are living in a global market. Usually, electronic or online services for translate paper don't work quite well for tech docs.

  20. dalexander
    December 21, 2011

    Mfbertozzi, Always good to hear from you. You reminded me of my early days at Fairchild R&D. I had three years of German under my belt and so I was tasked to translate technical documents written by German engineers. Some of those papers were really hard to convert to English because of a word like “voltaspannung” , meaning literally “fountain of volts” properly translates into electromotive force, or EMF, or simply voltage. So, I can see where translating tech docs would present a problem, especially in the text heavy sections. However, the units of measure, and electrical symbols are very uniform throughout the world so “uH” means micro Henry and Tphl means propagation delay low to high etc. So then one is left with the task of knowing what each measurement or characteristic the symbol or value applies to. Companies like Panasonic have Japanese Datasheets, but also publish the same Datasheets in English. Usually, if you contact a manufacturer and ask for a version in your language, they can help you with specific information, or will be willing to help you translate a document to your understanding. I can imagine the worst case scenario, where no one speaks, writes, or translates with any accuracy and the design is adversely impacted. I would be interested in hearing what your experience has been with this issue. Also, I would like to hear how anyone else has dealt with this. Any takers?

  21. dalexander
    December 21, 2011

    Tphl= Propagation delay high to low. Tplh is the low to high delay nemonic.

  22. mfbertozzi
    December 21, 2011

    Here we are. You are absolutely right, very good and professional perspective (as usual, from you). In general simbols for measurement are international and recognized abroad, personally I've felt very exciting experiences in translation for text within pages and numbers and dates. In a huge part of the world, people don't use Western calendar and numbers are not using Western digit, I would mention for example the Gulf region or China. In my case, the solution was to learn about local alphabetic, then I've had the chance for increase my knowledge, as per (I believe) your experience with German language.

  23. thetradezone
    December 21, 2011

    There are some great datasheet archive websites that store every revision of a datasheet and most application notes that refers to the part. It's useful to an engineer to have the complete data set to pick from.

    Every datasheet store in the world has huge gaps in their data. Especially PDF datasheets pre 2000. In the 90s datasheets and application notes would disappear from manufacturer websites and be gone forever.

  24. dalexander
    December 21, 2011
  25. mfbertozzi
    December 21, 2011

    Very good, useful and professional.

    Coming back to experiences, personally, when I've met with numerical expressions looking like

    ٤ ‎ – ٥

    for meaning 45, only way found was to learn fundamentals of foreign language. It was the sens of my previous post.

     

  26. dalexander
    December 21, 2011

    mfbertozzi,

    It looks like Greek to me. Epsilon and omicron or omega. I have never seen this meaning 45 degrees. Can you scan the datasheet and send it to my email at ? Anyone else ever see this? Epsilon usually means “Sum” in formulas. Maybe it is borrowed from another discipline like the building or construction business.

  27. dalexander
    December 21, 2011

    mbertozzi,

    So I zoomed in on your symbol and it looks like epsilon (small) or Sigma (large). I think the omicron is just the degree symbol common accross all usage. I suspect that the symbol was either a typo, or represented a quantity from an earlier calculation on the datasheet carried forward. It could be that it represents a summation of vectors or a non-conventional use for phase angle. I would really like to see that datasheet.

  28. dalexander
    December 21, 2011

    Correction: Sigma for “Sum”.

  29. dalexander
    December 21, 2011

    I have it. It is Arabic with the numbers ٤‎ – ٥‎ or 45. Done deal! Fun research.

  30. _hm
    December 22, 2011

    It is nice to work with parts from reputed semiconductor vendors. However, when one is to employ specialized semiconductor parts from small manufacturer, data is very limited. It is very difficult to enhance the circuit function in different topology. Designer task becomes very daunting.

     

     

  31. _hm
    December 22, 2011

    It is also important to read about parts information other then electrical and mechanical characteristics. RoHS compliance, country of origin (free from political troubles), long term stability of vendor and their financial health is also quite relevant in selecting vendor and parts.

     

  32. dalexander
    December 22, 2011

    -hm and All, http://www.componentsengineering.com/wp-content/uploads/pdfs/Sample-Request-Form-1.pdf This is one of two forms I use to save myself a lot of work in selecting or qualifying new or alternate source parts. It takes into consideration the advice of -hm and then some more key items. I give the factory or distributor rep this URL and ask them to complete the form and submit it with the sample parts they are offering. Together with the “Component Information Request” form, I am asking the person selling me the parts to do all the research before I can accept their samples. Questions like, ” How long have the parts been in production?” and “What are the reliability numbers?” etc., help me qualify both the part and supplier quickly. More importantly, it helps me disqualify the part and not have to spend unnecessary time in house with qualification procedures. The Reps fill out the forms and often discover the parts are not good alternates as Operating Characteristics may be different or unacceptable. Just give your supplier the URL every time they want to introduce a part and you will have a much easier time with sample part management and allowing or disallowing a supplier as well.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.