AD9516-4BCPZ Analog Devices Inc, AD9516-4BCPZ Datasheet - Page 25

• Manufacturer Part Number: AD9516-4BCPZ
• Description: Clock IC With 1.8GHz On-chip VCO
• Manufacturer: Analog Devices Inc
• Type: Clock Generator, Fanout Distributionr

Specifications of AD9516-4BCPZ

• Pll: Yes
• Input: Clock
• Output: CMOS, LVDS, LVPECL
• Number Of Circuits: 1
• Ratio - Input:output: 1:14
• Differential - Input:output: Yes/Yes
• Frequency - Max: 1.8GHz
• Divider/multiplier: Yes/No
• Voltage - Supply: 3.135 V ~ 3.465 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LFCSP
• Frequency-max: 1.8GHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD9516-4/PCBZ - BOARD EVAL FOR AD9516-4 1.8GHZ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TERMINOLOGY
Phase Jitter and Phase Noise
An ideal sine wave can be thought of as having a continuous
and even progression of phase with time from 0° to 360° for
each cycle. Actual signals, however, display a certain amount
of variation from ideal phase progression over time. This
phenomenon is called phase jitter. Although many causes can
contribute to phase jitter, one major cause is random noise,
which is characterized statistically as being Gaussian (normal)
in distribution.
This phase jitter leads to a spreading out of the energy of the
sine wave in the frequency domain, producing a continuous
power spectrum. This power spectrum is usually reported as a
series of values whose units are dBc/Hz at a given offset in
frequency from the sine wave (carrier). The value is a ratio
(expressed in dB) of the power contained within a 1 Hz
bandwidth with respect to the power at the carrier frequency.
For each measurement, the offset from the carrier frequency is
also given.
It is meaningful to integrate the total power contained within
some interval of offset frequencies (for example, 10 kHz to
10 MHz). This is called the integrated phase noise over that
frequency offset interval and can be readily related to the time
jitter due to the phase noise within that offset frequency interval.
Phase noise has a detrimental effect on the performance of
ADCs, DACs, and RF mixers. It lowers the achievable dynamic
range of the converters and mixers, although they are affected
in somewhat different ways.
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Time Jitter
Phase noise is a frequency domain phenomenon. In the time
domain, the same effect is exhibited as time jitter. When
observing a sine wave, the time of successive zero crossings
varies. In a square wave, the time jitter is a displacement of the
edges from their ideal (regular) times of occurrence. In both
cases, the variations in timing from the ideal are the time jitter.
Because these variations are random in nature, the time jitter is
specified in units of seconds root mean square (rms) or 1 sigma
of the Gaussian distribution.
Time jitter that occurs on a sampling clock for a DAC or an
ADC decreases the signal-to-noise ratio (SNR) and dynamic
range of the converter. A sampling clock with the lowest possible
jitter provides the highest performance from a given converter.
Additive Phase Noise
Additive phase noise is the amount of phase noise that can be
attributed to the device or subsystem being measured. The phase
noise of any external oscillators or clock sources is subtracted.
This makes it possible to predict the degree to which the device
impacts the total system phase noise when used in conjunction
with the various oscillators and clock sources, each of which
contributes its own phase noise to the total. In many cases, the
phase noise of one element dominates the system phase noise.
When there are multiple contributors to phase noise, the total is
the square root of the sum of squares of the individual contributors.
Additive Time Jitter
Additive time jitter is the amount of time jitter that can be
attributed to the device or subsystem being measured. The time
jitter of any external oscillators or clock sources is subtracted. This
makes it possible to predict the degree to which the device impacts
the total system time jitter when used in conjunction with the
various oscillators and clock sources, each of which contributes
its own time jitter to the total. In many cases, the time jitter of
the external oscillators and clock sources dominates the system
time jitter.
AD9516-4