Voltage Reference
4.1
Power Options
J10 is arranged as five rows, each of which can be shorted.
lists the power option details for J10.
For normal operation, J10.1-2, J10.3-4, and J10.5-6 must be connected (direct or through an ammeter),
and either (or both) of J10.7-8 and J10.9-10 must be connected; otherwise, the board will not function.
Table 4. J10 Configuration: Power Options
Row
Name
Function
1-2
ADC AVDD
AVDD supply current measurement point for the
ADC. Must be connected for operation.
3-4
ADC AVSS
AVSS supply current measurement point for the
ADC. Must be connected for operation.
5-6
ADC DVDD
DVDD supply current measurement point for the
ADC. Must be connected for operation.
7-8
DGND
Connects DGND to board ground.
9-10
AGND
Connects AGND to board ground.
5
Voltage Reference
The ADS1246 device always uses an external reference. The EVM provides a 2.048V reference for the
device from U1, filtered and buffered through U2. This 2.048V may be used to drive the REFP input, or
REFP can be connected to the external reference on J8 through switch S1. REFP should not be
connected to AVDD through switch S1 because this connection will violate the specification for the
maximum reference input.
shows switch S1 as it appears on the EVM. The low side of the
reference (REFN) is tied to AVSS. The different reference options under different supply conditions are
outlined in
Figure 1. Reference Select Switch S1
Table 5. Reference Voltage Options
AVDD
AVSS
J1 Setting
S1 Position
(1)
REFP
REFN
Reference Voltage
5V
0V
1-2
BUFF
2.048V
0V
2.048V
5V
0V
2-3
BUFF
0V
0V
Invalid Selection
5V
0V
—
Center
REF+ (J8.20)
0V
Up to AVDD
–
1
2.5V
–
2.5V
1-2
BUFF
–
0.452V
–
2.5V
2.048V
2.5V
–
2.5V
2-3
BUFF
0V
–
2.5V
2.5V
2.5V
–
2.5V
—
Center
REF+ (J8.20)
–
2.5V
Up to AVDD
–
AVSS
–
1
(1)
Switch S1 should not be set to AVDD.
6
ADS1146EVM, ADS1246EVM, ADS1146EVM-PDK, ADS1246EVM-PDK
SBAU149B
–
June 2009
–
Revised May 2011
Copyright
©
2009
–
2011, Texas Instruments Incorporated
