[SI-LIST] Re: Two Layer routing
- From: "Pommerenke, David" <davidjp@xxxxxxx>
- To: <rchundru_umr@xxxxxxxxx>, <sunil_bharadwaz@xxxxxxxxx>, "SI LIST" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 25 Apr 2007 19:30:05 -0500
Group,
=20
Designing two layer boards for SI and especially EMI is an art. Two =
hints might help:
=20
1) You can use slow signals as returns for fast ones by adding =
capacitors to the ends of the slow trace. This way it is an RF return =
(via the capacitors).
=20
2) Stiching the grounds together is the most important part for =
controlling the return currents. It may require using 7mil vias or alike =
and some traces might be bridged using zero Ohm resistors.=20
=20
A lot more time needs to be spend in understanding the optimal placement =
of components such that return currents can be controlled and that no, =
or as few as possible critical ground gaps occur.
=20
David Pommerenke
________________________________
From: si-list-bounce@xxxxxxxxxxxxx on behalf of Ram Chundru
Sent: Wed 4/25/2007 1:53 PM
To: sunil_bharadwaz@xxxxxxxxx; SI LIST
Subject: [SI-LIST] Re: Two Layer routing
Sunil,
With not a lot of field containment possible, both of them are much =
worse in a two layer board. Which one is more troublesome depends on the =
impedances of the source and the victim circuits. However, with all the =
large loops formed by the traces to route the signals, inductive =
crosstalk could be more troublesome. This also results in increased =
emissions and susceptibility too.
=20
Thanks,
Ram=20
sunil bharadwaz <sunil_bharadwaz@xxxxxxxxx> wrote:
Hi Friends ,
PCB routing in a two layer PCB with out power planes is definitely
not advisable.Noisy ,EMI .....
I believe cross talk will be worse too.Is the capacitive coupling
or the inductive coupling which makes the cross talk bad in the two =
layer
cases ?
Could some one pls explain this.
Thanks in advance!!
regards
Sunil . Bh
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Ram Chundru
System Level ESD Engineer
Texas Instruments Inc.
12500 TI Blvd, MS 8734
Dallas, TX 75243
Phone: 214-480-1654
www.emc-engineer.com
=20
=20
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