0
–10
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
–20 NO DITHER
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
0
5
10
15
20
25
30
FREQUENCY – MHz
Figure 20. 1M FFT Without Dither
100
90 ENCODE = 65MSPS
AIN = 15.5MHz
80 NO DITHER
70
60
50
40
30
SFDR = 90dB
REFERENCE LINE
20
10
0
–90 –80 –70 –60 –50 –40 –30 –20 –10 0
ANALOG INPUT POWER LEVEL – dBFS
Figure 21. SFDR Without Dither
95
2.2MHz
90 WORST SPUR
85
30.5MHz
ENCODE = 65MSPS
80
2.2MHz
SNR
75
30.5MHz
70
65
–15.0
–10.0
–5.0
0
5.0
10.0
15.0
ENCODE INPUT POWER – dBm
Figure 22. SNR, Worst Spurious vs. Clamped Encode
Power (See Figure 25)
AD6644
0
–10
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
–20 DITHER @ –19dBm
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
–130
0
5
10
15
20
25
30
FREQUENCY – MHz
Figure 23. 1M FFT with Dither
100
90 ENCODE = 65MSPS
AIN = 15.5MHz
80 DITHER = –19dBm
70
60
50
SFDR = 100dB
40
REFERENCE LINE
30
20
SFDR = 90dB
REFERENCE LINE
10
0
–90 –80 –70 –60 –50 –40 –30 –20 –10 0
ANALOG INPUT POWER LEVEL – dBFS
Figure 24. SFDR with Dither
REV. 0
–11–