Also, that paper you reference has actually been retracted.
https://ieeexplore.ieee.org/document/8114328
Nick Franconi
On Sat, Jun 5, 2021 at 11:12 AM Chuck Corley <corley@xxxxxxxxx> wrote:
Just to add something to that, in my post I was referring to EMI
(emissions).
There is also another side issue of crosstalk between traces that your
customer might possibly be thinking of. There is the possibility of
long serpentine traces increasing crosstalk between traces and causing
signals to fail. Especially if making space for the serpentine traces
causes the layout to pack traces closely together, making the crosstalk
worse.
Chuck
---
Chuck Corley
On 2021-06-04 21:01, Zachariah Peterson, NWES wrote:
Hi Chuck,https://www.researchgate.net/publication/321143234_Differential_Lines_Paired_with_Serpentine_as_Potential_EMI_Aggressors_in_Mobile_Electronic_Devices
That's exactly how it was done: only routing over a solid ground plane
with no gaps, so I'm unsure what my client could be referring to. I'm
now wondering if this is a case where the client got this idea because
someone did the routing incorrectly in the past (routing over a gap or
whatever), and then this guy is blaming in on the structure of
serpentine routing.
--
Zachariah Peterson
On 2021-06-04 20:49, Chuck Corley wrote:
Short answer: If you have a good plane ('reference plane') as you
should have under those traces to set the proper trace impedance
then they will couple to that plane and not significantly radiate.
If you didn't have a solid reference plane close under your traces
then you've built an antenna and they will radiate. Some people do
this accidentally, by having big gaps or other bad features in their
reference plane.
Chuck
---
Chuck Corley
On 2021-06-04 20:16, Zachariah Peterson, NWES wrote:
Hi everyone,
While I was conducting a design review today, my client expressed
some
concern over serpentine routing that was used to enforce length
matching
between an SDRAM chip running at 166 MHz (1 ns rise time) and an
MCU.
The concern was that the serpentine routing structure would create
an
EMI problem. The traces are routed according to specs in the
datasheet
with a reference plane on the adjacent layer.
I have never heard of serpentine routing creating a new EMI
problem or
making some existing EMI problem worse. I started looking into it
and I
find mixed recommendations. This is one instance where I won't
trust
application notes, they all give inconsistent guidance, and they
show
poor images of the exact way serpentine routing should be
implemented.
I looked into the literature and there are some studies on EMI,
effects
on eye diagrams, and reflections from serpentine routing
structures.
Here's one example:
------------------------------------------------------------------
If anyone can provide some perspective, or if someone can confirm
this
is just another signal integrity myth, I'd appreciate it. Thanks
in
advance.
--
Zachariah Peterson
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