Datasheet

AD7938/AD7939 Data Sheet
Rev. C | Page 12 of 36
V
REF
(V)
DNL (LSB)
4
3
1
2
0
–1
0.25 0.50 1.250.75 1.00 2.001.751.50 2.752.502.25
03715-012
SINGLE-ENDED MODE
POSITIVE DNL
NEGATIVE DNL
Figure 10. AD7938 DNL vs. V
REF
for V
DD
= 3 V
V
REF
(V)
EFFECTIVE NUMBER OF BITS
12
11
10
8
9
7
6
0 0.5 1.51.0 2.52.0 4.03.53.0
03715-013
V
DD
= 5V
DIFFERENTIAL MODE
V
DD
= 5V
SINGLE-ENDED MODE
V
DD
= 3V
SINGLE-ENDED MODE
V
DD
= 3V
DIFFERENTIAL MODE
Figure 11. AD7938 ENOB vs. V
REF
V
REF
(V)
OFFSET (LSB)
0
–0.5
–1.5
–1.0
–3.5
–3.0
–2.5
–2.0
–4.0
–4.5
–5.0
0 0.5 1.51.0 2.52.0 3.53.0
03715-014
SINGLE-ENDED MODE
V
DD
= 5V
V
DD
= 3V
Figure 12. AD7938 Offset vs. V
REF
CODE
???
10000
9000
7000
8000
3000
4000
5000
6000
2000
1000
0
2046 2047 2048 2049 2050
03715-015
DIFFERENTIAL MODE
3 CODES
INTERNAL
REF
9997
CODES
Figure 13. AD7938 Histogram of Codes for
10k Samples @ V
DD
= 5 V with the Internal Reference
RIPPLE FREQUENCY (kHz)
CMRR (dB)
60
70
80
100
90
110
120
0 200 400 800600 12001000
03715-017
DIFFERENTIAL MODE
Figure 14. CMRR vs. Ripple Frequency with V
DD
= 5 V and 3 V