[SI-LIST] Re: ESD is a low frequency event -really??
- From: MikonCons@xxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 9 Mar 2004 16:55:12 EST
In a message dated 3/8/2004 5:28:03 PM Pacific Standard Time,
Chris.Cheng@xxxxxxxxxxxx writes:
As for the BC comment, beside it being speculative, I can also make the top
and bottom reference planes to be ground and therefore don't need any plane
capacitance to provide the surface current to discharge.
I overlooked this comment in my response of a few moments ago. For
clarification, I too like to use reference planes on the available space on
both top and
bottom layers; however, my reference to BC to achieve tight high frequency
coupling between power and ground planes is far from speculative. The broadband
coupling forces all reference voltages and planes within which any given IC
and its associated signals are operating to move in synchronism with any
applied
or induced common-mode voltage. Hence, the IC operating environment
pertubation is the best one can obtain under the conditions of an ESD strike.
Please
recall that I stated earlier that BC is only one element of several
complementary techniques that may be used in combination to meet a given design
requirement.
There are many cases where, with careful and knowledgable layout (as Chris
has eloquently pointed out on many occasions), BC power/ground sandwiches are
NOT required; however, the need for a low impedance, well-decoupled power
distribution system (PDS) has been massively demonstrated in many threads on
the SI
List. BC is one approach that works well in this regard. I generally use BC
construction in critical applications that justify the extra cost, which
amounts
to ~60% of my designs (for over 80 different companies). And, I use BC for a
few more reasons than most designers to obtain extra margin in specific areas
that are critical to a given design.
Contrary to what one might infer, Chris and I are not in opposite camps, but
design in overlapping areas. For example, one of my (extreme) consulting tasks
involved designing PCBs, enclosures, interconnects and a grounding and
shielding system for a compact, very lightweight application that required the
system of three components to radiate over 60 dB less than FCC Class B levels.
Mike
Michael L. Conn
Owner/Principal Consultant
Mikon Consulting
Cell: (408)821-9843
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