On Tue, 14 Jan 2014 05:19:19 -0500, you wrote:
On 01/13/2014 12:43 PM, David wrote:
Thanks for that. So, basically, those thin traces are carrying low
voltage, low current signals, where the thicker traces tend to be higher
power carriers.
Mark
That is generally how it works and in this case, the power and ground traces
connected at the left and right sides of the edge connector are even thicker
than the thick signal traces which do not run between pins.
As an alternative to adding an inductor and/or resistor, sometimes power traces
have a deliberately thin section with decoupling at the ends to serve as a low
pass filter for controlling noise.
That would be presuming the noise is a low power component?
Mark
Usually this is done to remove switching noise such as that which would come
from a switching power supply or digital logic. What makes it effective versus
using an LC or RC filter is that the frequency content is high. In many cases,
an LC filter may have too much capacitive coupling from input to output to be
effective at high frequencies so in demanding applications, an LC filter is
followed by a printed circuit board filter which is less expensive than using a
lossy ferrite bead as a filter.
As a practical matter, adding a printed circuit board decoupling filter can mean
the difference between 50mV peak to peak of switching noise and 5mV peak to peak
of switching noise. A lossy ferrite bead would also work well.
David Hess