ICS83947AYI-147 ICST [Integrated Circuit Systems], ICS83947AYI-147 Datasheet - Page 5

• Manufacturer Part Number: ICS83947AYI-147
• Description: LOW SKEW, 1-TO-9 LVCMOS/LVTTL FANOUT BUFFER
• Manufacturer: ICST [Integrated Circuit Systems]

83947AYI-147
The spectral purity in a band at a specific offset from the funda-
mental 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 fun-
damental frequency to the power value of the fundamental. This
ratio is expressed in decibels (dBm) or a ratio of the power in
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-
Integrated
Circuit
Systems, Inc.
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
-100
-110
-120
-130
-140
-150
-160
-170
-180
-190
-10
-20
-30
-40
-50
-60
-70
-80
-90
-10
-20
-30
-40
-50
-60
-70
-80
-90
0
0
1k
1k
10k
10k
http://www.icst.com/products/hiperclocks.html
O
O
FFSET
FFSET
A
DDITIVE
F
F
ROM
ROM
100k
100k
C
C
ARRIER
ARRIER
P
Additive Phase Jitter, RMS
Additive Phase Jitter, RMS
HASE
5
156.25MHz (12KHz to 20MHz)
156.25MHz (12KHz to 20MHz)
the 1Hz band to the power in the fundamental. When the re-
quired offset is specified, the phase noise is called a dBc value,
which simply means dBm at a specified offset from the funda-
mental. 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.
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.
F
F
1M
1M
REQUENCY
REQUENCY
J
= 0.01ps typical @ 2.5V
= 0.02ps typical @ 3.3V
ITTER
LVCMOS/LVTTL F
(H
(H
10M
10M
Z
Z
)
)
@
@
100M
100M
ICS83947I-147
L
OW
REV. A SEPTEMBER 24, 2004
ANOUT
S
KEW
, 1-
B
UFFER
TO
-9