Re: Package descriptions--Take 1

Chris,

I'm in basic agreement with you. To respond in detail,
(>> denotes what Chris wrote):

>> Actually, both the transmission-line model and the lumped circuit
>> model assume a TEM mode. Non-TEM implies radiative loss, which no
>> lumped model can account for directly. Besides, the transmission
>> line model is equvalent to lumped circuits if the "lumps" are
>> distributed in a ladder in small enough pieces.

Depends on what you mean by "TEM"; if you mean no radiation, fine, I
agree. (Actually, you CAN define lumped circuit models that have
radiation in them, by including "retardation," but it's not worthwhile
until the frequencies get REALLY high or the packages VERY big.)

My point is simply that transmission line models for a single wire
alone in space are not possible. And transmission line models for
inherently wiggly 3-D stuff are not worth attempting.

>> I propose we use RLGC matricies to represent package parasitics
>> in the case where mutual parasitics between the pins must be
>> included. A banded-symmetric format for these parasitics could
>> be used to keep the number of entries down.

I propose the same thing; but I suggest we represent the matrices as a
SPICE deck. This is a well-known, industry standard format that
everyone understands. The symmetry is implicit in the SPICE. The
"banded" (or more generally, "sparse") nature of the matrix will be
there if you don't specify the coupling between far-off elements.
Finally, the SPICE provides flexibility to describe discontinuities
between bond wires, lead frame and pins.

--Eric
Received on Fri Oct 1 10:11:30 1993