OMAPL137-HT Datasheet, PDF (430/444 Pages) Texas Instruments – Multimedia Device

OMAP4460
Public Version
SWPS046A – JANUARY 2012
www.ti.com
A.4.2.4.2.1 Sdd11 / Sdd22
Sdd11 / Sdd22 represents the differential-mode return loss of the two lines. The ideal condition for the
interlane specification is to place the two lines far away from each other not to have any crosstalk. Then,
the ideal interlane Sdd11 / Sdd22 = 0, which is –∞ dB. Sdd11 / Sdd22 is recommended to be smaller than
the below line.
Interlane Sdd11/Sdd22
0
–10
–20
–30
–40
Frequency Sdd 11/Sdd 22
0.1 GHz > –40 dB
1 GHz
> –25 dB
–50
5 GHz
> –10 dB
–60
10²
10³
Frequency (GHz)
SWPS040-192
Figure A-31. Interlane Sdd11 / Sdd22 Frequency-domain Specification
If the designed differential lines have higher Sdd11 / Sdd22 than the specification, the differential lines can
be improved by two ways. One way is to adjust the space distance between the N and P lines of a
differential pair, and the other way is to put ground/power nets between the two lines to reduce the
crosstalk.
A.4.2.4.2.2 Scc11 / Scc22
Scc11 / Scc22 represents the common-mode return loss of the two lines. The ideal interlane Scc11 /
Scc22 =0, which is –∞ dB. Scc11 / Scc22 is recommended to be smaller than the below line. If the
designed differential lines have higher Scc11 / Scc22 than the specification, the differential lines can be
improved by putting ground/power nets between the two lines.
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