RE: EN55022:1995 vs EN55022:1998
Cyril, In reading the new standard one thing that caught my eyes is that Telecommunication ports are re-defined. In this case a Telecommunications is anything that hooks to a network i.e. LAN/WAN environments. For that reason alone I have to test to the new portion of the standard, but I am not required to do so in the immunity portion of testing. My two cents... Josh -Original Message- From: Binnom, Cyril A [mailto:binno...@ems-t.com] Sent: Wednesday, May 24, 2000 11:49 AM To: emc-pstc Subject: EN55022:1995 vs EN55022:1998 Group, I have some questions regarding EN 55022:1998. 1) Judging by what I have read it would seem that if your products are without telecommunication ports then you are already compliant to EN 55022:1998 since all changes to the new standard are telecommunication product based. 2) If question one is accurate then can the previous EN 55022:1995 data be used to update the Declaration of Conformity to the 1998 standard or does new data need to be taken? Thank you in advance for your help Cyril A. Binnom Jr. EMI/EMC Approvals Engineer (770) 447-4224 Ext.3240 (770) 447-6928 Fax e-mail binno...@lxe.com Visit Our Website at: http://www.lxe.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Quiet Expert
Group, I am in the process of evaluating an EMI analysis tool. The program is Quiet Expert by Innoveda (formally Viewlogic as I understand it). Is anyone using this program or have you evaluated it along with others? Dale --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re:RE: Charge moving from decoupling capacitors
Forwarded for George.. Reply Separator Subject:RE: Charge moving from decoupling capacitors Author: george_t...@dell.com List-Post: emc-pstc@listserv.ieee.org Date: 5/23/00 12:35 PM Let's say that you have a cap placed at 1/4 wavelength away from an IC pwr pin. When the IC draws current from the Pwr/gnd planes, it causes a voltage dip/pwr bounce on the parallel planes. This voltage dip propagates to the cap at 1/4 wavelength away and draws current out of the cap. The current from the cap propagates back to the IC pwr pin at 1/4 wavelength away. The total travel for the incident and reflected wave is 1/4 + 1/4 = 1/2 wavelength. The supply current is 180 degrees out of phase from the IC switching current. Some people say that the cap needs to be closer than 1/2 of rising edge. But you can also calculate the wavelength of the 3rd and 5th harmonic of your pulse to determine your cap placement. Regards, George Tang george_t...@dell.com -Original Message- From: Roncone Paolo [mailto:paolo.ronc...@compuprint.it] Sent: Tuesday, May 23, 2000 7:15 AM To: 'george_t...@dell.com '; 'barry...@altavista.com ' Cc: 'emc-p...@ieee.org ' Subject: RE: Charge moving from decoupling capacitors George, can you pls explain your correction ? I supposed your first statement (At 1/4 wavelength, the charges are 90 degrees out of phase) was the correct one ! Paolo Roncone Compuprint s.p.a. Reply Separator Subject:RE: Charge moving from decoupling capacitors Author: george_t...@dell.com List-Post: emc-pstc@listserv.ieee.org Date: 5/22/00 9:14 PM Barry, I need to make a correction. I was rushing to lunch on Thursday, so I did not read over what I wrote. Here is the correction for the 2nd comment below: At 1/4 wavelength, the charges are 180 degrees out of phase, so they are working against the IC current draw. 1/8 wavelength (90 degrees out of phase) is what I consider to be acceptable. Regards, George Tang george_t...@dell.com -Original Message- From: Tang, George Sent: Thursday, May 18, 2000 12:31 PM To: 'Barry Ma'; Tang, George Cc: si-l...@silab.eng.sun.com; emc-p...@ieee.org Subject: RE: Charge moving from decoupling capacitors Barry, Thanks for the comments. Here are my comments: Ok, you put caps at a certain distance away from the IC because you only want them to work at 100 MHz. But that distance turns out to be the 1/4 wave distance at 400 MHz, and you placed enough caps at the 1/4 wave distance to cause board resonance. Now what? Do you tell the caps not to work at 400 MHz because it's not their frequency? For your 2nd comment: I used the words loosely define for that reason. If you are interested in high frequency decoupling and instantaneous current, you really want to have all your charges moving in phase. At 1/4 wavelength, the charges are 90 degrees out of phase, so they will not do much for your instantaneous current. 1/8 wavelength is what I consider to be acceptable. You can certainly pick a different number. Regards, George Tang george_t...@dell.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
CISPR 24 and telecom ports
I am looking to see what the general conception is on I/O port conducted emissions and surge immunity is. The company I work for manufactures various types of network cards. Some of these tie to the outside word (public network) and others are LAN based. I can see performing the testing on ISDN and other style devices but not to a device, say and Ethernet card or a device, that does not access the public network directly. I have not read over the CISPR 24 document yet but based on what I have been told, the spec is vague on the areas of I/O ports and the outside world. Regards, Guy Story, KC5GOI Compliance Technician Interphase Corporation Dallas Texas phone: 214.654.5161 fax: 214.654.5406 --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
EN55022:1995 vs EN55022:1998
Group, I have some questions regarding EN 55022:1998. 1) Judging by what I have read it would seem that if your products are without telecommunication ports then you are already compliant to EN 55022:1998 since all changes to the new standard are telecommunication product based. 2) If question one is accurate then can the previous EN 55022:1995 data be used to update the Declaration of Conformity to the 1998 standard or does new data need to be taken? Thank you in advance for your help Cyril A. Binnom Jr. EMI/EMC Approvals Engineer (770) 447-4224 Ext.3240 (770) 447-6928 Fax e-mail binno...@lxe.com Visit Our Website at: http://www.lxe.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Fwd: Split Plane
Subject: RE: [SI-LIST] : Split Plane To: si-l...@silab.eng.sun.com From: Barry Ma barry...@altavista.com List-Post: emc-pstc@listserv.ieee.org Date: 24 May 2000 10:51:29 PDT Another reason, I guess, is that you are not confident to use pwr planes as signal return planes. You said: We pulled out all the stops to ensure every signal layer is referenced to a ground plane, rather than a power plane, which I understand should give better EMC performance. I'd like to say it again, it's OK to use pwr planes if you have enough interplane capacitance. Regards, Barry Ma b...@anritsu.com On Wed, 24 May 2000, Brad Crowell wrote: Christoph I agree with your suggestion and we did consider this but the additional cost was the overriding factor. Brad -Original Message- From: owner-si-l...@silab.eng.sun.com Sent: Wednesday, May 24, 2000 10:29 AM To: si-l...@silab.eng.sun.com Subject: RE: [SI-LIST] : Split Plane Brad, Did you think about doing this job using MicroVia technology? In this case you would be able to cover the top and bottom layer with ground, as the Fanout-Vias are in the pad. So the top and bottom ground plane will be real planes over the whole board! Then the stackup could look like this: GND Signal Signal 3.3V GND Signal Signal GND 5V Signal Signal GND Because of the MicroVias, you will be able to route much more effective, as they don't block other layers - perhaps you can even save one or two signal layers. If you are looking for good EMI performance, this would be a good idea. Christoph Hillen Utimaco Safeware AG Germany ___ Why pay when you don't have to? Get AltaVista Free Internet Access now! http://jump.altavista.com/freeaccess4.go ___ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: ISM prohibited frequencies
Hello Jenkins, As long as the levels in the restricted bands are below the limits specified in 15.209, you should be okay. No frequency (fundamental or harmonic or 'internal functioning') within a restricted band can exceed the levels specified in 15.209. Regards, Bandele Jetstream Communications, Inc. badep...@jetstream.com -Original Message- From: JENKINS, JEFF [mailto:jeff.jenk...@aei.com] Sent: Wednesday, May 24, 2000 7:38 AM To: emc-p...@majordomo.ieee.org Subject: ISM prohibited frequencies I have a question about ISM prohibited frequencies according to 47 CFR Part 18. Section 18.303 says that operation in the prohibited frequency bands is not allowed. My question is, what is their interpretation of the word operation? 1.) If the equipment in question uses these frequencies only for internal functioning, is it still prohibited? (In other words, the energy does not intentionally leave the equipment enclosure.) 2.) If the equipment sweeps through a prohibited band while it auto-tunes, is this a problem? 3.) What if the fundamental operating frequency of the equipment is outside the prohibited bands, but there is significant harmonic energy within a prohibited band? Thanks, Jeff Jenkins Regulatory Compliance Advanced Energy Industries, Inc. Fort Collins, CO USA --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: ISM prohibited frequencies
I asked the same questions of the FCC a couple of years ago and was told (reply your Q): (2)The sweep-through wasn't necessarily a problem if powered operation was not possible within the prohibited bands. (3)Harmonics...(partly my interpretation)then you are responsible to assure that emissions are 10uV/m @ 1600m for these emissions (1) internal (entirely my own...) The FCC are concerned with interference with emergency/rescue services; if your oscillators' signals are contained, there can be no interference. HTH --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Fwd: [SI-LIST] : Announcement, new book
--- Start of forwarded message --- To: si-l...@silab.eng.sun.com Subject: [SI-LIST] : Announcement, new book From: Doug Brooks d...@eskimo.com List-Post: emc-pstc@listserv.ieee.org Date: Tue, 23 May 2000 16:18:43 -0700 UltraCAD has just published its new book Electrical Engineering for the Non-Degreed Engineer The book is specifically written for people in the PCB design, fabrication and assembly industry and covers the basics of EE up through impedance and RLC phase shifts. Although most of you on this list don't need a book like this, I believe you all work with people who COULD use it. It has already been adopted for class use in one of the Community Colleges in Texas. You can review the book and the table of contents on our web site, http://www.ultracad.com Thanks Doug Brooks . Doug Brooks' book Electrical Engineering for the Non-Degreed Engineer is now available. See our web site for details. . Doug Brooks, President d...@eskimo.com UltraCAD Design, Inc. http://www.ultracad.com --- End of forwarded message --- ___ Why pay when you don't have to? Get AltaVista Free Internet Access now! http://jump.altavista.com/freeaccess4.go ___ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
ISM prohibited frequencies
I have a question about ISM prohibited frequencies according to 47 CFR Part 18. Section 18.303 says that operation in the prohibited frequency bands is not allowed. My question is, what is their interpretation of the word operation? 1.) If the equipment in question uses these frequencies only for internal functioning, is it still prohibited? (In other words, the energy does not intentionally leave the equipment enclosure.) 2.) If the equipment sweeps through a prohibited band while it auto-tunes, is this a problem? 3.) What if the fundamental operating frequency of the equipment is outside the prohibited bands, but there is significant harmonic energy within a prohibited band? Thanks, Jeff Jenkins Regulatory Compliance Advanced Energy Industries, Inc. Fort Collins, CO USA --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: Evaluation Boards
John, For developmental boards the pertinent paragraphs of CFR47 immediately follow the text you transcribed. FCC clearly exempts boards used for development at a customer facility under paragraphs (v) and (2), however the marking requirement applies. (iv) Evaluation of product performance and determination of customer acceptability, provided such operation takes place at the manufacturer's facilities during developmental, design, or pre-production states; or (v) Evaluation of product performance and determination of customer acceptability where customer acceptability of a radio frequency device cannot be determined at the manufacturer's facilities because of size or unique capability of the device, provided the device is operated at a business commercial, industrial, scientific, or medical user's site, but not at a residential site, during the development, design or pre-production stages. A product operated under this provision shall be labeled, in a conspicuous location with the notice in paragraph (c) of this section. (2) For the purpose of paragraphs (e)(1)(v) of this section, the term 'manufacturer's facilities' includes the facilities of the party responsible for compliance with the regulations and the manufacturer's premises, as well as the facilities of other entities working under the authorization of the responsible party in connection with the development and manufacture, but not marketing, of the equipment. 'Marketing' is subject to interpretation; many companies have technical marketing departments with their own development labs. My interpretation: to demonstrate ~ in front of customers, the marketing paragraphs apply. David __ Reply Separator _ Subject: RE: Evaluation Boards Author: jestuckey SMTP:jestuc...@micron.com at ADEMCONET List-Post: emc-pstc@listserv.ieee.org Date:5/23/2000 10:56 AM I had forwarded this to Vic upon receiving his request last week, but viewing some on the responses that I have seen, I feel it would be appropriate to put it out for general viewing. Look at 47 CFR 2.803 Marketing of radio frequency devices prior to equipment authorization. (a) Except as provided elsewhere in this section, no person shall sell or lease, or offer for sale or lease (including advertising for sale or lease), or import, ship, or distribute for the purpose of selling or leasing or offering for sale or lease, any radio frequency device unless: (1) In the case of a device subject to certification, such device has been authorized by the Commission in accordance with the rules in this chapter and is properly identified and labeled as required by 2.925 and other relevant sections in this chapter; or (2) In the case of a device that is not required to have a grant of equipment authorization issued by the Commission, but which must comply with the specified technical standards prior to use, such device also complies with all applicable administrative (including verification of the equipment or authorization under a Declaration of Conformity, where required), technical, labeling and identification requirements specified in this chapter. (b) The provisions of paragraph (a) of this section do not prohibit conditional sales contracts between manufacturers and wholesalers or retailers where de-livery is contingent upon compliance with the applicable equipment authorization and technical requirements, nor do they prohibit agreements between such parties to produce new products, manufactured in accordance with designated specifications. (c) Notwithstanding the provisions of paragraphs (a), (b), (d) and (f) of this section, a radio frequency device may be advertised or displayed, e.g., at a trade show or exhibition, prior to equipment authorization or, for devices not subject to the equipment authorization requirements, prior to a determination of compliance with the applicable technical requirements provided that the advertising contains, and the display is accompanied by, a conspicuous notice worded as follows: This device has not been authorized as required by the rules of the Federal Communications Commission. This device is not, and may not be, offered for sale or lease, or sold or leased, until authorization is obtained. (1) If the product being displayed is a prototype of a product that has been properly authorized and the prototype, itself, is not authorized due to differences between the prototype and the authorized product, the following disclaimer notice may be used in lieu of the notice stated in paragraph (c) introductory text of this section: Prototype. Not for sale. (2) Except as provided elsewhere in this chapter, devices displayed under the provisions of paragraphs (c) introductory
Re: interference to Comm devices due to overhead catenaries
Susan: Are the catenaries enrgized? In any event you can expect some signal degradation and perhaps complete cancellation as the locomotive moves becuase the catenaries will screen the GPS signals. As you may be aware, GPS relies on a minimum of two visible satellite signals and sometimes is able to see six or more which makes accuracy more achievable. Any metallic medium interspersed between the GPS antenna and the direct satellite signal will cause a certain attenuation to the signal. Can you provide more specifics? Ralph Cameron EMC Consultant for Suppression of Consumer Electronics (After Sale) - Original Message - From: Beard, Susan sbe...@ge-harris.com To: emc-p...@ieee.org Sent: Tuesday, May 23, 2000 3:56 PM Subject: interference to Comm devices due to overhead catenaries Could anyone provide any information relative to overhead catenary noise and its affects on locomotive roof top comm systems (e.g., GPS)? Susan Beard --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: Concerning DoC and RTTE
The way I read my fresh new copy of the New Blue Guide thanks to Art Michael and others yesterday the paragraph immediately preceding the snip included below by Kim tells the story. I am sorry that I can't include the text verbatim but my copy is PDF format. The paragraph defines products that must be accompanied by the EC DoC as gas appliances, potentially explosive atmospheres, recreational craft, lifts, and high speed rail. This reflects into the paragraph included by Kim where it is defined that these DoC's that must accompany the product must be in the language of the country of use. It is implied that other than the mentioned directives it is OK to use only one of the languages of the Member States. I would interpret this to mean one language is OK for RTTE DoC's and that the DoC need not accompany the product with each shipment. Are there any other opinions out there because this is only one man's opinion? Having heard on this board some comments that some Member States prefer having DoC's with each shipment (ITE and RTTE), I am considering having a copy of the DoC included with the product manual in English. Does anyone see a problem in following this approach? The intent is to include an exact replica of the DoC with a statement in the signature area defining the location of the original signed DoC. Jim Allan Senior Compliance Engineer Milgo Solutions Inc. E-mail james_al...@milgo.com -Original Message- From: k...@i-data.com [SMTP:k...@i-data.com] Sent: Wednesday, May 24, 2000 4:19 AM To: emc-p...@majordomo.ieee.org; t...@world.std.com Subject: Concerning DoC and RTTE Dear All: I'm still confused by the answers I have got concerning the languages of the DoC. I still understand what I'm reading as if I need to provide the DoC in all legal EU language if I want to sell my product in all EU countries. Here are my references: RTTE directive (L91/16) Article 6 3. Member States shall ensure that the manufacturer or the person responsible for placing the apparatus on the market provides information for the user on the intended use of the apparatus, together with the declaration of conformity to the essential requirements. This is taken from page 60 of the New Blue Guide The EC declaration of conformity must be drawn up in one of the official languages of the Community. If the Community directives contain no further provisions concerning the language of the declaration, the requirements of the Member States to use a specific language must be assessed according to Art. 28 and 30 of the EC Treaty, on a case by case basis. However, for products, which are required to be accompanied by the declaration of conformity, it has to be in the official language of the country of use. In these situations a translation should be provided by the manufacturer, his authorised representative or the distributor. Additionally, a copy of the declaration in the original language should be supplied. Please help me ? I would like to use only 1 or 2 languages if possible. Best regards, Kim Boll Jensen i-data international Denmark --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Concerning DoC and RTTE
Dear all I'm still confused by the answers I have got concerning the languages of the DoC. I still understand what I'm reading as if I need to provide the DoC in all legal EU language if I want to sell my product in all EU countries. Here are my references: RTTE directive (L91/16) Article 6 3. Member States shall ensure that the manufacturer or the person responsible for placing the apparatus on the market provides information for the user on the intended use of the apparatus, together with the declaration of conformity to the essential requirements. This is taken from page 60 of the New Blue Guide The EC declaration of conformity must be drawn up in one of the official languages of the Community. If the Community directives contain no further provisions concerning the language of the declaration, the requirements of the Member States to use a specific language must be assessed according to Art. 28 and 30 of the EC Treaty, on a case by case basis. However, for products, which are required to be accompanied by the declaration of conformity, it has to be in the official language of the country of use. In these situations a translation should be provided by the manufacturer, his authorised representative or the distributor. Additionally, a copy of the declaration in the original language should be supplied. Please help me ? I would like to use only 1 or 2 languages if possible. Best regards, Kim Boll Jensen i-data international Denmark --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Breakdown voltage between pcb layers
In a message dated 5/23/00, David Gelfand writes: We have an emissions problem on a board and I would like to suggest a ground plane in the area of an RJ-45 jack (TNV-1). But we have always asked our PCB designers to leave TNV traces free of ground and power planes to avoid arcing during surge and dialectric strength tests. Does anyone know where to find specs on breakdown voltages between PCB layers? Has anyone successfully used ground planes above or below TNV traces? We are testing to UL1950 and Part 68. David: I do not think it is a good idea to put ground plane under your TNV-1 circuits. It is possible to do this, but I do not recommend it. You do not mention the type of EMC problem you are trying to resolve, but if it is an emissions problem, the first choice would be to add a common mode choke in series with tip/ring. If that alone is not sufficient, you can sometimes add small value caps (100 pF or so) from tip to chassis and from ring to chassis. Since these capacitors bridge the isolation barrier, they must be suitable high voltage caps. Capacitors in these locations can be very helpful if you have a quiet metal chassis to connect them to, but they are useless and even potentially harmful for EMC if the product has only a plastic housing with no real chassis. When adding capacitors, you must also watch out for detrimental effects on the intended signal. If you are still intent on adding a ground plane under your TNV-1 circuit, the main requirement for both FCC Part 68 and UL 1950 will be to pass a 1000 VRMS hipot test. You can do this by carefully specifying the required insulation between the relevant layers, but now your board stack-up will be subject to special requirements that both you and your board vendor must keep track of. Another potential problem is that TNV vias which pass through the ground plane must have a large enough clearance hole in the ground plane to avoid hipot failures at that point. There is one special case where the requirements of the above paragraph are easy to meet. This would be when the TNV circuits are on the top layer and the ground plane is on the bottom layer, with no copper on any of the internal layers. In this case, the entire thickness of the board is insulation, which is more than adequate. However, as soon as you start using the inner layers, you must get involved with specifying the layer-to-layer dielectric strength. While the overall thickness of the board is always specified, individual board fabricators typically exercise considerable freedom in selecting the thickness of the insulation between inner layers. In summary, I do not think it is a good idea to extend your ground plane under the TNV circuits, but it is technically possible to do so by carefully specifying the circuit board stack-up. Before you resort to this solution, I think you should carefully examine the reasons why this seems to be necessary, and consider alternative solutions. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. http://www.randolph-telecom.com --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
