4.1

Power Options

5

Voltage Reference

Voltage Reference

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J10 is arranged as five rows, each of which can be shorted. Table 4 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.

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. Figure 1 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 Table 5.

Figure 1. Reference Select Switch S1

Table 5. Reference Voltage Options

AVDD

AVSS

J1 Setting

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

SBAU149A – June 2009 – Revised July 2009

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