The technical notes are listed by number and can be copied for distribution to customers requesting application information. Due to copyright restrictions, only the technotes written by Wurth Electronics Midcom staff or those that have been approved by the author/publisher are available for download.  A condensed list of our technical list is also available.

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Certain publishers have agreed to allow us to reprint some of the articles on a limited basis. If you are interested in receiving a reprint, e-mail or fax us your request indicating the TechNote number or numbers in which you are interested. Note that some of them are lengthy, so please limit your request to those for which you have immediate need only. If fulfilling your request would require an inordinate amount of faxed sheets, (say more than 15 pages) please provide your mailing address so we can send them to you via mail.

TN11 - DC Holding Circuits

Developed by Wurth Electronics Midcom staff members, this TN features several DC Loop Holding Circuits (7-pages). One of them meets the UK voltage/current template as specified by NET4. The article may also be downloaded in Microsoft Word format, TN11.doc and TN11pt2.doc
Source: LeVasseur, D., & Stoos, M., (1993, July 12). DC holding circuits. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN14 - Leakage Inductance vs. Winding Splits

This is piece came from a working project that required a specific amount of leakage inductance. Splitting the windings once did not give enough leakage inductance and winding without splits gave too much. The empirical results match a mathematical function very closely. Although this note is mainly for use internal to Wurth Electronics Midcom, some customers may be interested in it as well. This article is downloadable in .pdf format.
Source: Winterton, D., (1991, October 4). Leakage inductance vs. winding splits. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN16 - Transducer Loss Measurement Using A Network/Spectrum Analyzer

With the increasing availability of dual-input measurement systems, many of our customers are interested in automated insertion loss measurement methods.
Available for  download in .pdf format.
Source: LeVasseur, D., (1991, October). Transducer loss measurement using a network/spectrum analyzer having dual voltmeter inputs. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN17 - Transformer Equivalent Circuit

This is the 'complete' equivalent circuit as used in Wurth Electronics Midcom's Transformer Analysis Program (TAP). Parameter numbers are shown for reference to the program.  A version of TAP is planned for the web site as well. The  License Agreement is available in pdf format. Once you have downloaded and printed the license agreement, sign it and fax to us at +1.605.886.4486, attention: Wurth Electronics Midcom Marketing.
Source: Staff (1991, March). TAP agreement. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)
 

TN18 - Calculating Modem Transformer Insertion Loss

This is an easy method to calculate transmit insertion loss based on a few transformer parameters. The result is a 7 page treatise that uses only the resistive losses of the transformer model (neglects the reactive effects) and is usually close enough for most applications. As a result, this note may be appended in the future to include the 'inductance vs. mismatch' curves from Reuben Lee's and Nathan Grossner's texts.
Source: LeVasseur, D., (1991, October). Calculating modem transformer insertion loss. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)
 

TN19 - A Wet DAA for Rockwell Fax/Modem Chips

This one page application note may help customers needing a very basic DAA (Data Access Arrangement). It highlights Wurth Electronics Midcom's 671-8001 and 671-8005.
Source: Marcroft, D., (1991, October 17). Application note for Rockwell RC224ATF and RC9624DP ICs. (Available from Rockwell International Corp., PO Box C, Newport Beach, CA 92658-8902)
 

TN23 - Impedance measurements of telephone lines

This two page TN shows the impedances measured on the telephone line running from a residence in Mankato, MN on January 7, 1984 to each of several 'quiet termination' lines in the Mankato area. The results show fairly smooth transitional impedance change over frequency with all measurements being predominantly capacitive in their reactance. Other data taken shows the impedances measured when the same 'quiet termination' numbers were called through the Wurth Electronics Midcom PBX. Results under this condition show marked change in impedance with frequency. Wiltron return loss measurements were also taken and recorded. The article may be downloaded in Microsoft Word format, TN23.doc
Source: LeVasseur, D., (1984, January). Impedance measurements of telephone lines. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)
 

TN30 - "Tax" pulse frequencies by country

This is a short list of the metering 'tax' pulse or billing tone frequencies used in various countries.
Source: LeVasseur, D., (1992, August). Tax pulse frequencies for various countries. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN33 - dBm to RMS Voltage Chart, Excel and  PDF versions

This Excel spreadsheet or PDF document may be printed as a chart showing various voltages and power levels in dBm for impedances popular in the telecom world.
Source: Staff, (1993, December). dBm to RMS voltage chart. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN34 - Return Loss Test Method 999-2318 and Summary Schematic

This document shows how to measure return loss during the application of DC to the device under test. The transformer specified by 999-2318 is 671-0023. If you would also like one of these transformers for comparison purposes, e-mail our sales department or contact your Wurth Electronics Midcom representative. See also TN35, TN37. This TN is available for download in  .pdf format.
Source: Staff, (1993, February). Return loss test method 999-2318 and summary schematic. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN35 - VOM Measures Complex Impedances

This TN shows how to measure both magnitude and phase of an impedance using a standard VOM (also known as 'Z-box'). This TN contains a BASIC program to assist with the number crunching. The program also calculates return loss of the calculated impedance for a given reference network. An Excel spreadsheet and a BASIC program are included to automate calculations. A zip file, TN35.zip, contains the Excel spreadsheet, the BASIC programs, images of the schematic and voltage vector diagram explaining the principle behind Z-Box and the text article. Incidentally, this was the inception of a 'Design Idea' article in EDN (February 9, 1984).
Source: Bipes, J., (1984). VOM Measures Complex Impedances. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN37 - Return Loss Calculations

This TN explains how return loss can be determined from resistance and reactance measurements. This TN contains a MathCad analysis, an Excel spreadsheet analysis and a QuickBASIC program listing. A zip file, TN37.zip, contains the Excel spreadsheet and the BASIC programs. Return loss calculations can be made versus a purely resistive reference (e.g., 600 ohms) , a resistance in series with a capacitance (e.g., 600 ohms in series with a 2.15 uF capacitor), or any of the three-element complex networks that are commonly used in Europe (e.g., Germany's 220 ohm + 820 ohm || 115 nF). See also TN34, TN35.
Source: Staff, (1993, July). Return Loss Calculations. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN43 - Tax Pulse Product Summary

This summary shows all of Wurth Electronics Midcom's tax pulse filter products. Available for  download in .pdf format.
Source: Staff, (1995). Tax pulse product summary. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN54 - How to measure Total Harmonic Distortion

This is a short guide describing the test method used to measure Total Harmonic Distortion (THD) of a transformer or other passive device as practiced at Wurth Electronics Midcom. Use of an HP-339A or equivalent distortion analyzer is presumed. Available for download in pdf format, TN54.pdf
Source: LeVasseur, D., (1994, June 29). Transformer distortion test method using an HP-339A or equivalent. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN67 -    Handling Guidelines

These brief, how-to-handle guidelines are provided to help our customers obtain the best performance from their Wurth Electronics Midcom products.  Also includes recommendations for IR reflow temperature profile and tips on water washing.  Source: Staff, (1995). Handling guidelines. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN69 -   Transformer Theory Seminar Notes

This is the companion handout to Wurth Electronics Midcom's 'The Telecommunications Transformer: Low Cost Solution to Product Reliability and Continuing Regulatory Compliance' seminar by our Chief Technical Officer, Dave LeVasseur. The most recent of this document, completed July 1, is available in .pdf format. This version runs about 70 pages and about 832K.

TN79 -   Overview of IEC 950 - EN 60950 (BABT), UL 1950 / CSA 950

In the words of the author, this is "a brief overview of what it is, and what is important when dealing with transformers." It is a summary of the impact of IEC 950 and related documents on telecommunications safety with specific emphasis on how this impacts the telecom line interface transformer. The piece includes definitions of applicable safety terms such as hazardous voltage, ELV and SELV.
Source: Pedersen, M., (1997, May 29). Overview of IEC 950, EN 60950 (BABT), UL1950/CSA 950. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN82 -   Transformer Modeling Tips

January 8, 1998. 11 pages. If you can't obtain the equivalent circuit for a transformer, but you have a sample of it, this technical note will help you drive its equivalent circuit. You will need access to basic lab equipment and an impedance bridge to perform the tests described.  Source: LeVasseur, D., (1998, January 8). Transformer Modeling Tips. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN83 -    3750 V of Isolation Not Required at the Network Termination

April 28, 1998. 2 pages. This technical note by Mel Pedersen, Wurth Electronics Midcom Homologations Engineer, briefly explains the origin of the 3750 VAC requirement, and why it no longer applies to information technology equipment especially at the Network Termination. It also contains the current network isolation requirements for analog telephone equipment.  Source: Pedersen, M., (1998, April 27). 3750 V of Isolation Not Required at the Network Termination. (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN84 - Constants in transformer equations: effect of wave shapes

November 19, 1998. 13 pages. The basic transformer equation contains a constant which takes on a value of 4.44 when the transformer is excited by a sinewave and 4.0 when it is presented with a squarewave. This technical note shows where the 4.44 and 4.0 values are derived -- a source of puzzlement on part of more than a few engineers. Source: LeVasseur, D., (1998, November 19). Constants in transformer equations: effect of wave shapes. Also  TN84.pdfavailable in PDF (Available from Wurth Electronics Midcom, 121 Airport Drive, Watertown, SD 57201-6330)

TN85 -  Scrapless Laminations

November 17, 1998. Short presentation on lamination tooling and how scrapless laminations are made. Describes a few of the noticeable features exhibited by scrapless laminations exhibit that are not found on other laminations. Source: LeVasseur, D., (1998, November 17).

TN88 -  CTR-21 DAA

December 2, 1999.  This technical note is really an application note featuring a DAA circuit developed by Joe Randolph of Randolph Telecom.  The DAA is designed to meet the requirements of Europe's CTR-21 and with minor modifications can also be used in North America.  The DAA incorporates a Wurth Electronics Midcom 82107 transformer which is suitable for low speed modem applications such as V.22bis, V.29 (fax) and perhaps even up to V.32bis (14.4 kb/s).

TN89 -  ADSL / POTS Splitter Application Drawing

January 5, 2001 by Jim Vanover, Wurth Electronics Midcom Engineering.  Application note showing a typical ADSL / POTS splitter filter incorporating Wurth Electronics Midcom 40101 and 40109 coupled inductors, a 40159 common-mode choke and the capacitors needed to provide proper filtering.

TN90 - EIA Date Code Spreadsheet

January 16, 2001.  This spreadsheet was created for use by manufacturers  like Wurth Electronics Midcom who adhere to the EIA or Mil-Std-1285 date code method.  It generates a sheet of the two-digit codes corresponding to the week a product is manufactured.  The method used to determine the week number is based on the Mil-Std-1285 rule that the first week of the year is the one in which the first Thursday falls.    This leads to some interesting situations such as a 53rd week in some years, or a week 1 of manufacture that actually starts the last week of December of the prior year.  (For example, week 1 of manufacturing year 1998 started on December 28th, 1997)

TN91 -   IEC 60950 and Its History - Explained

November, 1999 - Revised April, 2000.  By Mel Pedersen, Wurth Electronics Midcom Homologations Engineer. IEC 60950 (formerly IEC 950) is a safety standard written by the International Electro-technical Commission (IEC).  In particular, IEC 60950 is a standard for the Safety of Information Technology Equipment (ITE). This standard covers safety requirements for a broad range of products including Personal Computers, Telecommunication Equipment (both Customer Premise, Central Office, and Network Equipment), Modems, Fax Machines, Copiers & Printers, even Pencil Sharpeners.  Many countries use IEC 60950 as a basic outline or recommendation from which they derive their own ITE safety standards. Each national version deviates from IEC 60950 in order that particular issues or safety concerns specific to that country’s electrical codes and Power Distribution Systems are addressed.

TN92 -   Current Sense Transformer Resistor Selection

June 13, 2001  By Byron Thomas, Wurth Electronics Midcom, Inc.  Two common ways to measure switched DC current in a circuit is by using a current sense transformer or a resistor. Both work in a similar fashion but the current sense transformer provides isolation between the IC and the input or output power line. The resistor also injects losses into the circuit.

TN94 -   FLEXformer^TM Product Lines Features, Applications, Packaging

January 16, 2002   By Byron Thomas, Wurth Electronics Midcom, Inc.  The FLEXformer^TM product lines were designed as flexible lines of transformers and inductors in low profile EFD packages. There are hundreds of different designs that are possible from just 12 standard products. You can configure the pins of the transformer to get the results that meet your requirements. This flexibility provides you with a unique, customized product while maintaining the benefits of an off-the-shelf product.

TN95 -  TN95 - Transformer UL Recognition:

October 4, 2000   By Mel Pedersen, Wurth Electronics Midcom, Inc.  The current UL 1459 requirements for Telecommunications Equipment remain certified until 1 April 2005 at which time the new requirements of the UL 60950/CSA 60950 will begin. This paper addresses Wurth Electronics Midcom's recognition for the more strigent UL 60950/CSA 60950 requirements.

TN98 -  Low Cost Telephone Line Interface(DAA, FXO)

March 17, 2005 By Joe Randolph of Randolph telecom.  This Technical Note is an update to an earlier Technical Note that was written in 1999.  The earlier version was TN #88, “Low Cost, CTR 21 Compliant DAA for Europe.”  The European regulatory requirement CTR 21 has now been officially withdrawn.  Some manufacturers prefer to continue meeting CTR 21, but there is little reason to do so.  The design presented in TN #88 can be updated to make it less expensive and also more broadly applicable worldwide.

TN99 -  NEETS Introduction to AC and Transformers

Navy Electricity and Electronics Training Series Module 2 - Introduction to Alternating current and Transformers. This is a single module of a 24 module self-study course developed by the US Navy. This particular module covers alternating current and transformers.