Datasheet

AD9222 Data Sheet
Rev. F | Page 32 of 60
External Reference Operation
The use of an external reference may be necessary to enhance
the gain accuracy of the ADC or improve thermal drift charac-
teristics. Figure 82 shows the typical drift characteristics of the
internal reference in 1 V mode.
When the SENSE pin is tied to AVDD, the internal reference is
disabled, allowing the use of an external reference. The external
reference is loaded with an equivalent 6 kΩ load. An internal
reference buffer generates the positive and negative full-scale
references, REFT and REFB, for the ADC core. Therefore, the
external reference must be limited to a nominal of 1.0 V.
0 1.00.5 2.01.5 3.02.5 3.5
V
REF
ERROR (%)
CURRENT LOAD (mA)
05727-083
–30
–5
–10
–15
–20
–25
5
0
Figure 81. V
REF
Accuracy vs. Load, AD9222-50
0.02
–0.18
–0.14
–0.10
–0.06
–0.02
–0.16
–0.12
–0.08
–0.04
0
–40
V
REF
ERROR (%)
TEMPERATURE (°C)
05967-028
–20 0 20 40 60 80
Figure 82. Typical V
REF
Drift, AD9222-50