I agree. In fact it is no engineering at all. Cut and try is no engineering either. > > On the subject of adding caps in circuits for noise immunity. Rather than > just throwing in a value of 0.1 uF, finding it works, and calling it good I > like to use a different approach. Determine the lowest value that will fix > the immunity problem. Then find the largest value that will still allow the > circuit to function properly. Then specify a value somewhere in between; > possibly the geometric mean. In this way you are not using a value "next to > a cliff" that will cause some malfunction in a production run. In a high > volume product just throwing in a value and calling it good is EXTREMELY > poor engineering. > > Dave Cuthbert > Micron Technology > > -----Original Message----- > From: [email protected] [mailto:[email protected]] > Sent: Thursday, January 16, 2003 8:19 PM > To: [email protected] > Subject: Re: I2C bus sensitivity to EFT > > > > I have never worked on design of a product with external I2C bus, but > considering the bus speed of 100 kHz to 3.4 MHz (depending on type) relative > to > about 60-100 MHz BW (depending on definition) of EFT, you may try killing > good > portion of EFT with ceramic caps. > > Be sure that the cable shield is connected on both ends. > > Also, check for the possibility that the EFT may couple to some other > apparently non-critical pin of the IC and then internally cause > susceptibility. > The first suspect in such case would be the reset pin, but often you can be > surprised that other pins may cause problems. I just had a case in which EFT > > would couple to the LED driver on an Ethernet device and cause problems > internally in the chip, leading to packet loss. A cap on the LED driver pin > fixed the problem !! :) > > Neven > > > > Hi Forum, > > Has anyone on this forum worked with I2C products and maybe be able to > > advise on the best method to suppress EFT noise that would alow the I2C > bus, > > via external cables, to operate as expected e.g. Good EFT devices? How > best > > to shield the I2C? Other? > > As always I look forward to your proffesional advice. > > History > > I have a system that connects 3 products (powered from an in-line external > > non-earthed power supply, SELV) using the I2C bus via a 1m shielded and 1m > > shielded curly cable. I use an I2C bi-directional extender IC P82B715 on > one > > of the products. The I2C protocol gets corrupted when I appply the > > Electrical Fast Transient (EFT) Test per the EMC Standard EN61000-4-4. > > I have tried shielded cables, several EFT devices and 1nF caps on the > lines > > but with little affect. > > > > Kind Regards > > Alex McNeil > > Principal Engineer > > Tel: +44 (0)131 479 8375 > > Fax:+44 (0)131 479 8321 > > email: [email protected] > > > > > > ------------------------------------------- > > This message is from the IEEE EMC Society Product Safety > > Technical Committee emc-pstc discussion list. > > > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > > > To cancel your subscription, send mail to: > > [email protected] > > with the single line: > > unsubscribe emc-pstc > > > > For help, send mail to the list administrators: > > Ron Pickard: [email protected] > > Dave Heald: [email protected] > > > > For policy questions, send mail to: > > Richard Nute: [email protected] > > Jim Bacher: [email protected] > > > > All emc-pstc postings are archived and searchable on the web at: > > http://ieeepstc.mindcruiser.com/ > > Click on "browse" and then "emc-pstc mailing list" > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list" > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://ieeepstc.mindcruiser.com/ > Click on "browse" and then "emc-pstc mailing list"
This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
