ICS85454-01 Datasheet, PDF (5/15 Pages) Integrated Circuit Systems – DIFFERENTIAL-TO-LVDS MULTIPLEXER

Integrated
Circuit
Systems, Inc.
ICS85454-01
DUAL 2:1/1:2
DIFFERENTIAL-TO-LVDS MULTIPLEXER
ADDITIVE PHASE JITTER
The spectral purity in a band at a specific offset from the
fundamental compared to the power of the fundamental is
called the dBc Phase Noise. This value is normally expressed
using a Phase noise plot and is most often the specified plot
in many applications. Phase noise is defined as the ratio of
the noise power present in a 1Hz band at a specified offset
from the fundamental frequency to the power value of the
fundamental. This ratio is expressed in decibels (dBm) or a
ratio of the power in the 1Hz band to the power in the funda-
mental. When the required offset is specified, the phase noise
is called a dBc value, which simply means dBm at a specified
offset from the fundamental. By investigating jitter in the fre-
quency domain, we get a better understanding of its effects
on the desired application over the entire time record of the
signal. It is mathematically possible to calculate an expected
bit error rate given a phase noise plot.
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
10
100
Additive Phase Jitter at
622.08MHz (12kHz - 20MHz)
= 0.05ps (typical)
1k
10k
100k
1M
OFFSET FROM CARRIER FREQUENCY (HZ)
10M
100M
As with most timing specifications, phase noise measure-
ments have issues. The primary issue relates to the limita-
tions of the equipment. Often the noise floor of the equipment
is higher than the noise floor of the device. This is illustrated
above. The device meets the noise floor of what is shown, but
can actually be lower. The phase noise is dependant on the
input source and measurement equipment.
85454AK-01
www.icst.com/products/hiperclocks.html
5
REV. B JUNE 16, 2006