ICS83947I-147 Datasheet, PDF (5/10 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-9 LVCMOS/LVTTL FANOUT BUFFER

Integrated
Circuit
Systems, Inc.
ICS83947I-147
LOW SKEW, 1-TO-9
LVCMOS/LVTTL FANOUT BUFFER
ADDITIVE PHASE JITTER
The spectral purity in a band at a specific offset from the funda- the 1Hz band to the power in the fundamental. When the re-
mental compared to the power of the fundamental is called the quired offset is specified, the phase noise is called a dBc value,
dBc Phase Noise. This value is normally expressed using a which simply means dBm at a specified offset from the funda-
Phase noise plot and is most often the specified plot in many mental. By investigating jitter in the frequency domain, we get a
applications. Phase noise is defined as the ratio of the noise better understanding of its effects on the desired application over
power present in a 1Hz band at a specified offset from the fun- the entire time record of the signal. It is mathematically possible
damental frequency to the power value of the fundamental. This to calculate an expected bit error rate given a phase noise plot.
ratio is expressed in decibels (dBm) or a ratio of the power in
0
-10
Additive Phase Jitter, RMS @
-20
156.25MHz (12KHz to 20MHz)
-30
= 0.02ps typical @ 3.3V
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
1k
10k
100k
1M
10M
100M
OFFSET FROM CARRIER FREQUENCY (HZ)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
1k
Additive Phase Jitter, RMS @
156.25MHz (12KHz to 20MHz)
= 0.01ps typical @ 2.5V
10k
100k
1M
10M
OFFSET FROM CARRIER FREQUENCY (HZ)
100M
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 de-
vice 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.
83947AYI-147
http://www.icst.com/products/hiperclocks.html
REV. A SEPTEMBER 24, 2004
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