Datasheet
ADuC814
Rev. A | Page 15 of 72
Figure 13 and Figure 14 show typical FFT plots for the ADuC814.
These plots were generated using an external clock input via
P3.5 to achieve coherent sampling. The ADC is using its internal
reference (2.5 V) sampling a full-scale, 10 kHz sine wave test
tone input at a sampling rate of 149.79 kHz. The resultant FFTs
shown at 5 V and 3 V supplies illustrate an excellent 100 dB
noise floor, a 71 dB signal-to-noise ratio (SNR), and a THD
greater than −80 dB.
20
0
–20
–40
–60
–80
–100
–120
–140
–160
dBs
20
FREQUENCY (kHz)
1007060504030
02748-A-020
AV
DD
/DV
DD
= 5V
f
S
= 149.79kHz
f
IN
= 9.910kHz
SNR = 71.3dB
THD = –88.0dB
ENOB = 11.6
Figure 13. ADuC814 Dynamic Performance at V
DD
= 5 V
20
0
–20
–40
–60
–80
–100
–120
–140
–160
dBs
20
FREQUENCY (kHz)
1007060504030
02748-A-021
AV
DD
/DV
DD
= 3V
f
S
= 149.79kHz
f
IN
= 9.910kHz
SNR = 71.3dB
THD = –88.0dB
ENOB = 11.6
Figure 14. ADuC814 Dynamic Performance at V
DD
= 3 V
Figure 15 and Figure 16 show typical dynamic performance
versus external reference voltages. Again excellent ac performance
can be observed in both plots with some roll-off being observed
as V
REF
falls below 1 V.
EXTERNAL REFERENCE (V)
50
0.5
SNR (dBs)
1.0 2.0 2.5 5.0
55
1.5
60
65
70
75
80
THD (dBs)
–100
–95
–90
–85
–80
–75
–70
AV
DD
/DV
DD
= 5V
f
S
= 152kHz
SNR
THD
02748-A-022
Figure 15. Typical Dynamic Performance vs. V
REF
, V
DD
= 5 V
EXTERNAL REFERENCE (V)
SNR (dBs)
80
75
65
50
70
55
AV
DD
/DV
DD
= 3V
f
S
= 152kHz
0.5 1.5 2.5
THD (dBs)
SNR
THD
60
–70
–75
–85
–100
–80
–95
–90
1.0 2.0 3.0
02748-A-023
Figure 16. Typical Dynamic Performance vs. V
REF
, V
DD
= 3 V