Datasheet

Data Sheet AD7938/AD7939
Rev. C | Page 11 of 36
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C, unless otherwise noted.
SUPPLY RIPPLE FREQUENCY (kHz)
PSRR (dB)
–
60
–70
–80
–90
–110
–100
–120
10 210 610410 810 1010
03715-007
100mV p-p SINE WAVE ON V
DD
AND/OR V
DRIVE
NO DECOUPLING
DIFFERENTIAL/SINGLE-ENDED MODE
INT REF
EXT REF
Figure 4. PSRR vs. Supply Ripple Frequency Without Supply Decoupling
NOISE FREQUENCY (kHz)
ISOLATION (dB)
–
70
–75
–90
–85
–80
–95
0 100 400200 300 600500 800700
03715-021
INTERNAL/EXTERNAL REFERENCE
V
DD
=5V
Figure 5. AD7938 Channel-to-Channel Isolation
FREQUENCY (kHz)
SINAD (dB)
80
70
60
50
40
30
20
0 100 400200 300 600500 1000700 800 900
03715-008
F
SAMPLE
=1.5MSPS
RANGE = 0 TO V
REF
DIFFERENTIAL MODE
V
DD
=5V
V
DD
=3V
Figure 6. AD7938 SINAD vs. Analog Input Frequency
for Various Supply Voltages
FREQUENCY (kHz)
0
–10
–20
–50
–40
–30
–90
–100
–80
–70
–60
–110
0
100 200 300 400 500 600 700
03715-009
4096 POINT FFT
V
DD
=5V
F
SAMPLE
=1.5MSPS
F
IN
= 49.62kHz
SINAD = 70.94dB
THD = –90.09dB
DIFFERENTIAL MODE
AMPLITUDE (dB)
Figure 7. AD7938 FFT @ V
DD
= 5 V
CODE
DNL ERROR (LSB)
1.0
0.8
0.6
0.4
0.2
–0.2
0
–0.8
–0.6
–0.4
–1.0
0 500 20001000 1500 30002500 40003500
03715-010
V
DD
=5V
DIFFERENTIAL MODE
Figure 8. AD7938 Typical DNL @ V
DD
= 5 V
CODE
INL ERROR (LSB)
1.0
0.8
0.6
0.4
0.2
–0.2
0
–0.8
–0.6
–0.4
–1.0
0 500 20001000 1500 30002500 40003500
03715-011
V
DD
=5V
DIFFERENTIAL MODE
Figure 9. AD7938 Typical INL @ V
DD
= 5 V