Datasheet
AD7940
Rev. A | Page 9 of 20
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 5 shows a typical FFT plot for the AD7940 at 100 kSPS
sample rate and 10 kHz input frequency. Figure 6 shows the
signal-to-(noise + distortion) ratio performance versus the
input frequency for various supply voltages while sampling at
100 kSPS with an SCLK of 2.5 MHz.
Figure 7 shows a graph of the total harmonic distortion versus
the analog input frequency for various supply voltages, while
Figure 8 shows a graph of the total harmonic distortion versus
the analog input frequency for various source impedances (see
the Analog Input section). Figure 9 and Figure 10 show the
typical INL and DNL plots for the AD7940.
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(dB)
–140
–120
–100
–80
–60
–40
–20
–160
0 10k 20k 30k 40k
FREQUENCY (kHz)
50k
0
V
DD
= 4.75V
F
SAMPLE
= 100kSPS
F
IN
= 10kHz
SNR = 84.48dB
SINAD = 84.35dB
THD = –98.97dB
SFDR = –100.84dB
Figure 5. AD7940 Dynamic Performance at 100 kSPS
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SINAD (dB)
80
85
75
10
INPUT FREQUENCY (kHz)
100
90
F
SAMPLE
= 100kSPS
T
A
= 25
°
C
V
DD
= 5.25V V
DD
= 4.75V
V
DD
= 2.5V
V
DD
= 4.3V
V
DD
= 3.6V
V
DD
= 3V
V
DD
= 2.7V
Figure 6. AD7940 SINAD vs. Analog Input Frequency
for Various Supply Voltages at 100 kSPS
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THD (dB)
90
100
80
10
INPUT FREQUENCY (kHz)
100
110
85
95
105
F
SAMPLE
= 100kSPS
T
A
= 25
°
C
V
DD
= 3V
V
DD
= 2.7V
V
DD
= 4.3V
V
DD
= 2.5V
V
DD
= 5.25V
V
DD
= 4.75V
V
DD
= 3.6V
Figure 7. AD7940 THD vs. Analog Input Frequency
for Various Supply Voltages at 100 kSPS
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THD (dB)
90
100
70
75
10
INPUT FREQUENCY (kHz)
100
110
85
80
95
105
F
SAMPLE
= 100kSPS
T
A
= 25
°
C
V
DD
= 4.75V
R
IN
= 10Ω
R
IN
= 50Ω
R
IN
= 100Ω
R
IN
= 1000Ω
Figure 8. AD7940 THD vs. Analog Input Frequency
for Various Source Impedances