Jim, I have not had to use ferrite chip hats myself, though I can think of applications OTHER than IC's where a sheet of ferrite would be handy -- if I could afford it. Apparently the chip hats suppress radiation from the top of a device large enough to be an effective radiator.
I see as limits to their usefulness the size of the chip, which reduces its effectiveness as a radiator at the ordinary (<GHz) harmonic frequencies, where there is more to be radiated, and the volume of ferrite, which being small seems more suited to suppress only high (GHz+) frequencies. But this is a common shortcoming for ferrite applications. If I were dealing with 500 MHz devices I might welcome them with open arms -- but I am not (yet). Cortland ====================== Original Message Follows ==================== >> Date: 02-Apr-99 11:05:02 MsgID: 1067-74026 ToID: 72146,373 From: "Knighten, James L" >INTERNET:[email protected] Subj: RE: RE: Ferrite pads vendors Chrg: $0.00 Imp: Norm Sens: Std Receipt: No Parts: 1 To All: Regarding these layers of ferrites that can be placed either above, or below an IC, a few people have indicated that "they work." Can anyone be more specific? What does it mean that "they work?" Jim Dr. Jim Knighten e-mail: [email protected] <mailto:[email protected]> Senior Consulting Engineer NCR 17095 Via del Campo San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com> Tel: 619-485-2537 Fax: 619-485-3788 --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
