[gta02-core] Audio ECN update

Werner Almesberger werner at openmoko.org
Wed Sep 2 09:13:15 CEST 2009

Rene Harder wrote:
> This kind of EMI suppression filter is what i think we are looking for:
> TDK MEM2012P101R
> http://www.tdk.co.jp/tefe02/e9617_mem_p.pdf

And they even have them at Digi-Key :-) So that one would be good
for data and audio ?

They're a little bulk, though. Also, when I compare the attenuation
plots of the MEM2012 (pi) and the Murata NFL18ST (tee), then they
basically look the same.

We've been over EMI filters a lot in the Dash/HXD8 project, because
of the high demands on GPS, and we had to switch from one type to
the other (on UART lines) because of sourcing, apparently without
ill effects.

Back then, I didn't understand what the real difference between the
two was. Maybe now I found someone who can explain ? ;-) What is
there that the data sheet doesn't tell us ? You mention impedance,
but all the data sheets show is attenuation for 50 Ohm.

- Werner

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