Datasheet

AD6644
Rev. D | Page 11 of 24
FREQUENCY (MHz)
0
–120
–130
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
(dBFS)
0 5 10 15 20 25 30
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
NO DITHER
00971-016
Figure 16. 1M FFT Without Dither
WORST-CASE SPURIOUS (dBc)
90
50
10
0
40
70
20
30
60
80
100
ANALOG INPUT POWER LEVEL (dBFS)
ENCODE = 65MSPS
AIN = 15.5MHz
NO DITHER
SFDR = 90dB
REFERENCE LINE
–90 –80 –70 –60 –50 –40 –30 –20 –10 0
00971-017
Figure 17. SFDR Without Dither
ENCODE = 65MSPS
30.5MHz
ENCODE INPUT POWER (dBm)
SNR, WORST SPURIOUS (dB and dBc)
80
70
65
85
95
75
WORST SPUR
90
2.2MHz
2.2MHz
30.5MHz
SNR
–15 –10 –5 0 5 10 15
0
0971-018
Figure 18. SNR, Worst Spurious vs. Clamped Encode Power (See
Figure 27)
FREQUENCY (MHz)
0
–120
–130
–110
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
ENCODE = 65MSPS
AIN = 15.5MHz @ –29.5dBFS
DITHER @ –19dBm
(dBFS)
0 5 10 15 20 25 30
00971-019
Figure 19. 1M FFT with Dither
WORST-CASE SPURIOUS (dBc)
90
50
10
0
40
70
20
30
60
80
100
ANALOG INPUT POWER LEVEL (dBFS)
ENCODE = 65MSPS
AIN = 15.5MHz
DITHER = –19dBm
SFDR = 100dB
REFERENCE LINE
SFDR = 90dB
REFERENCE LINE
–90 –80 –70 –60 –50 –40 –30 –20 –10 0
00971-020
Figure 20. SFDR with Dither