Datasheet

AD7944
Rev. A | Page 10 of 28
0 250 500 750 1000 1250
–180
–160
–140
–120
–100
–80
–60
–40
–20
0
FREQUENCY (kHz)
AMPLITUDE (dB)
04658-111
f
S
= 2.5MSPS
f
IN
= 20kHz
SNR = 84.65dB
THD = –100dB
SINAD = 84.5dB
Figure 11. FFT Plot (External Reference)
04658-112
12.0
12.5
13.0
13.5
14.0
14.5
15.0
78
79
80
81
82
83
84
2.5 3.0 3.5 4.0 4.5 5.0
ENOB (Bits)
SNR, SINAD (dB)
REFERENCE VOLTAGE (V)
SINAD
ENOB
SNR
Figure 12. SNR, SINAD, and ENOB vs. Reference Voltage
04658-113
80.0
80.5
81.0
81.5
82.0
82.5
83.0
83.5
84.0
84.5
85.0
1 10 100 1000
SINAD (dB)
FREQUENCY (kHz)
Figure 13. SINAD vs. Frequency
0 250 500 750 1000 1250
–180
–160
–140
–120
–100
–80
–60
–40
–20
0
FREQUENCY (kHz)
AMPLITUDE (dB)
f
S
= 2.5MSPS
f
IN
= 20kHz
SNR = 84dB
THD = –102dB
SINAD = 84dB
04658-114
Figure 14. FFT Plot (Internal Reference)
04658-115
–105
–104
–103
–102
–101
–100
2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00
THD (dB)
REFERENCE VOLTAGE (V)
Figure 15. THD vs. Reference Voltage
04658-116
–110
–105
–100
–95
–90
–85
–80
1 10 100 1000
THD (dB)
FREQUENCY (kHz)
Figure 16. THD vs. Frequency