Sir This serial "bus" is not intended to be used external to a PWB. The "II" means inter-IC. Noise/EFT immunity for I2C I/O external to the PWB is problematic. Noise/EFT immunity for I2C external to an unit's chassis is, well, even more problematic...
I am not aware of any CPU-based I2C or chipset intended to handle other than logic-level signals. Good Luck, Brian -----Original Message----- From: Alex McNeil [mailto:[email protected]] Sent: Tuesday, January 29, 2002 9:40 AM To: [email protected] Subject: EFT problem with I2C Serial Bus Hi Group, To those of you who are familiar with the I2C Serial Bus. Have you experienced a similar problem, as described below, with EN55024 mains EFT noise? I know it can be misleading to try and resolve a problem over the internet, but you can never tell....... I need to attach a 4way 2metre lengfh of cable to my product I2C Bus output to supply a peripheral. When I apply the mains EFT pulse at > 500V the product, with this new cable only attached and no peripheral, hangs. I have diagnosed the problem down to this cable picking up the EFT radiated noise from the AC SELV output cable (input to the product) of the 230Vac/10Vac power supply. When I remove the I2C i.e. the SDA and SLC lines, within the product, the product passes the EFT. When I re-attach either of these signals the system hangs. This was just to further prove the I2C bus was causing the problem. The product passed the EFT 2KV pulse with no I2C cable attached. Also, I cannot alter the power supply. I have tried various solutions on the PCB, all to my disappointment: Ferrites on cables Varied series resistor values on the SDA and SLC (22R to 330R) Varied series ferrite values on the SDA and SLC BAV99 (2 serial "fast" signal diodes package hanging on the lines) 100pf caps hanging on the lines Note: My product is a Class II (no earthing), all plastic. I would appreciate any comments? 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
