Datasheet

Reference

2-3

Analog Interface

2.2 Reference

The ADS8381EVM provides an onboard 4.096-V reference circuit.

This reference voltage can be applied directly to the VREF pin of the

converter; it does not need to be buffered. The EVM also has provi-

sion for a user-supplied external reference voltage. This voltage can

be filtered, as needed, by routing the signal through amplifier U1.

The EVM allows users to select from two reference sources. Set

SJP1 and SJP2 to select onboard reference voltage (REF3040), or

a user-supplied reference voltage via P1 pin 20. See Table 2−2 for

jumper settings. See Chapter 6 for the full schematic.

Table 2−2.Solder Short Jumper Setting

Reference

Jumper Setting

Reference

Designator

Description

1−2 2−3

SJP1 Select REF3040 output for reference voltage Installed

†

Select buffered reference voltage Installed

SJP2 Select U3, REF3040, as 4.096-V reference Installed

†

Buffer the user−supplied reference voltage Installed

SJP3 Short (−)IN pin to ground Installed

†

N/A

SJP4 Apply offset voltage to A/D buffer Installed

†

N/A

SJP5

Set amplifier U1 negative supply to ground Installed

Set amplifier U1 negative supply to −V

Installed†

SJP6

Set amplifier U2 negative supply to ground Installed

Set amplifier U2 negative supply to −V

Installed

†

Factory-set condition