Datasheet

AD7490 Data Sheet
Rev. D | Page 8 of 28
TYPICAL PERFORMANCE CHARACTERISTICS
Figure 5 shows a typical FFT plot for the AD7490 at 1 MSPS sample rate and 50 kHz input frequency.
Figure 7 shows the power supply rejection ratio vs. supply ripple frequency for the AD7490. The power supply rejection ratio is defined as
the ratio of the power in the ADC output at full-scale frequency f, to the power of a 200 mV p-p sine wave applied to the ADC V
DD
supply
of frequency f
S
.
( )








×=
s
Pf
Pf
PSRR log10dB
where:
Pf is equal to the power at frequency f in ADC output.
Pf
S
is equal to power at frequency f
S
coupled onto the ADC V
DD
supply input.
Here, a 200 mV p-p sine wave is coupled onto the V
DD
supply. 10 nF decoupling was used on the supply, and a 1 µF decoupling capacitor
was used on the REF
IN
pin.
5
–95
–75
–55
–35
–15
0 50
100 150 200
250 300 350
400 500450
8192 POINT FFT
f
SAMPLE
= 1MSPS
f
IN
= 50kHZ
SINAD = 70.697dB
THD = –79.171dB
SFDR = –79.93dB
02691-004
FREQUENC
Y (kHz)
SNR (dB)
Figure 5. Dynamic Performance at 1 MSPS
75
55
60
65
70
10 100 1000
02691-005
INPUT FREQUENCY (kHz)
SINAD (dB)
f
S
= MAX THROUGHPUT
T
A
= 25°C
RANGE = 0V TO REF
IN
V
DD
= V
DRIVE
= 5.25V
V
DD
= V
DRIVE
= 4.75V
V
DD
= V
DRIVE
= 3.6V
V
DD
= V
DRIVE
= 2.7V
Figure 6. SINAD vs. Analog Input Frequency
for Various Supply Voltages at 1 MSPS
–20
–90
–80
–70
–60
–50
–40
–30
0
100k 200k 300k
400k 500k 600k 700k 800k
900k 1M
02691-006
INPUT FREQUENC
Y (Hz)
PSRR (dB)
V
DD
= 5V
V
DD
= 3V
V
DD
= 3V/5V
, 10nF CAP
200mV p-p SINE WA
VE ON V
DD
REF
IN
= 2.5
V, 1µF CAP
T
A
= 25°C
Figure 7. PSRR vs. Supply Ripple Frequency
–50
–90
–85
–80
–75
–70
–65
–60
–55
10 100 1000
02691-007
INPUT FREQUENCY (kHz)
THD (dB)
V
DD
= V
DRIVE
= 2.7V
V
DD
= V
DRIVE
= 3.6V
V
DD
= V
DRIVE
= 4.75V
V
DD
= V
DRIVE
= 5.25V
f
S
= MAX THROUGHPUT
T
A
= 25°C
RANGE = 0V TO REF
IN
Figure 8. THD vs. Analog Input Frequency
for Various Supply Voltages at 1 MSPS