CN-0109 Datasheet, PDF (2/3 Pages) Analog Devices – Low Jitter Sampling Clock Generator for High Performance ADCs

CN-0109
Circuit Note
slew rate. Note that rms jitter values consistently less than 1 ps
can be achieved using the AD9858 circuit.
These circuits must be constructed on multilayer PC boards
with large area ground planes using proper grounding, layout,
and decoupling techniques (see MT-031 Tutorial, Grounding
Data Converters and Solving the Mystery of AGND and DGND
and MT-101 Tutorial, Decoupling Techniques) in order to
achieve these performance levels. Consult the evaluation board
documentation for the AD9958, AD9858, AD9515, and
AD6645 for more guidance.
Table 1. Jitter Response of AD9958 and AD9515 vs. fOUT, Power, Frequency, and Filter BW
Product
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
AD9958/AD9515
DDS
Sample
Rate (MHz)
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
500
DDS Output
Frequency
(MHz)
38.88
38.88
38.88
38.88
38.88
38.88
77.76
77.76
77.76
77.76
77.76
77.76
155.52
155.52
155.52
155.52
DDS Output
Power
(dBm)
−3.6
−3.6
−4.7
−4.7
−3.3
−3.3
−3.8
−3.8
−4.9
−4.9
−3.8
−3.8
−5.5
−5.5
−5.6
−5.6
DDS
Reconstruction
Filter (MHz)
200 LPF
200 LPF
47 LPF
47 LPF
5% BPF
5% BPF
200 LPF
200 LPF
85 LPF
85 LPF
5% BPF
5% BPF
200 LPF
200 LPF
5% BPF
5% BPF
AD9515
Divider Output
Setting
1
2
1
2
1
2
1
2, 4
1
2, 4
1
2, 4
2
4, 8
2
4, 8
AD9515 Output
Frequency
(MHz)
38.88
19.44
38.88
19.44
38.88
19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
Jitter
(rms)
(ps)
4.1
4.1
2.4
2.4
1.5
1.5
2.5
2.5
1.5
1.5
1.1
1.1
1.5
1.5
0.68
0.68
Table 2. Jitter Response of AD9858 and AD9515 vs. fOUT, Power, Frequency, and Filter BW
Product
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
AD9858/AD9515
DDS
Sample
Rate (MHz)
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
DDS Output
Frequency
(MHz)
155.52
155.52
155.52
155.52
155.52
155.52
155.52
155.52
155.52
155.52
155.52
155.52
DDS Output
Power (dBm)
+7.7
+7.7
+7.7
+7.7
+2.6
+2.6
+1.1
+1.1
−3.2
−3.2
−4.6
−4.6
DDS
Reconstruction
Filter (MHz)
225 LPF
225 LPF
5% BPF
5% BPF
225 LPF
225 LPF
5% BPF
5% BPF
225 LPF
225 LPF
5% BPF
5% BPF
AD9515
Divider Output
Setting
2
4,8
2
4, 8
2
4, 8
2
4, 8
2
4, 8
2
4, 8
AD9515 Output
Frequency (MHz)
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
77.76
38.88, 19.44
Jitter
(rms)
(ps)
0.56
0.56
0.33
0.33
0.63
0.63
0.42
0.42
0.73
0.73
0.64
0.64
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