ICS8535I-31 Datasheet, PDF (6/15 Pages) Integrated Device Technology – LOW SKEW, 1-TO-4, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V LVPECL FANOUT BUFFER

ICS8535I-31
LOW SKEW, 1-TO-4, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V LVPECL FANOUT BUFFER
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 fundamental. 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 frequency 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
Additive Phase Jitter @ 155.52MHz
-20
12kHz to 20MHz = 0.057ps (typical)
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
1k
10k
100k
1M
10M
100M
Offset Frequency (Hz)
As with most timing specifications, phase noise measurements
have issues. The primary issue relates to the limitations 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.
IDT™ / ICS™3.3V LVPECL FANOUT BUFFER
6
ICS8535AGI-31 REV. A AUGUST 16, 2007