AD9228
0.20
0.15
0.10
0.05
0
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 67 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.
–0.05
–0.10
–0.15
–0.20
–40
–20
0
20
40
60
80
5
TEMPERATURE (°C)
Figure 67. Typical VREF Drift
0
–5
–10
–15
–20
–25
–30
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
CURRENT LOAD (mA)
Figure 66. VREF Accuracy vs. Load
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