AD6644ST/PCB Analog Devices Inc, AD6644ST/PCB Datasheet - Page 17

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AD6644ST/PCB

Manufacturer Part Number
AD6644ST/PCB
Description
BOARD EVAL ADC 14BIT CMOS AD6644
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD6644ST/PCB

Rohs Status
RoHS non-compliant
Number Of Adc's
1
Number Of Bits
14
Sampling Rate (per Second)
65M
Data Interface
Parallel
Inputs Per Adc
1 Differential
Input Range
2.2 Vpp
Power (typ) @ Conditions
1.3W @ 65MSPS
Voltage Supply Source
Analog and Digital
Operating Temperature
-25°C ~ 85°C
Utilized Ic / Part
AD6644
Lead Free Status / Rohs Status
Not Compliant
Jitter Considerations
The signal-to-noise ratio (SNR) for an ADC can be predicted.
When normalized to ADC codes, Equation 1 accurately
predicts the SNR based on three terms. These are jitter, average
DNL error, and thermal noise. Each of these terms contributes
to the noise within the converter (see Equation 1).
where:
f
t
and internal encode circuitry).
ε is the average DNL of the ADC (typically 0.41 LSB).
n is the number of bits in the ADC.
V
of the ADC (typically 2.5 LSB).
ANALOG
j rms
NOISE rms
is the rms jitter of the encode (rms sum of encode source
SNR
is the analog input frequency.
is the V rms thermal noise referred to the analog input
=
20
V
NOISE
×
2
log
n
rms
⎛ +
1
2
2
n
ε
1
2 /
2
+
(
2
π
×
f
ANALOG
×
t
j
rms
)
2
+
Rev. D | Page 17 of 24
(1)
For a 14-bit ADC like the AD6644, aperture jitter can greatly
affect the SNR performance as the analog frequency is
increased. Figure 31 shows a family of curves that demonstrates
the expected SNR performance of the AD6644 as jitter increases
and is derived from Equation 1.
For a complete review of aperture jitter, see Application Note
AN-756, Sampled Systems and the Effects of Clock Phase Noise
and Jitter, at www.analog.com.
80
75
70
65
60
55
0
AIN = 110MHz
0.1
Figure 31. SNR vs. Jitter
0.2
JITTER (ps)
AIN = 150MHz
0.3
AIN = 30MHz
AIN = 190MHz
0.4
AIN = 70MHz
0.5
AD6644
0.6

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