Texas Instruments ADS1259EVM, User Manual

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Voltage Reference
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Between the power-supply input connector of J11 and the devices on the EVM, jumper J10 allows a point
to either bypass the supply connection or measure the supply current. With all the jumpers in J10 inserted,
the components on the EVM are powered through the power-supply header. In this configuration, AVDD =
+5V, DVDD = +3.3V, and AGND and DGND are both 0V (AGND and DGND are connected together on
the EVM). Jumper J10 is shown in
Figure 4 .
Figure 4. Jumper J10
Note that the high-voltage supplies for the PGA280 can only be accessed through pins 1 and 2 of jumper
J11. The suVA and –VA can be set to +10V to +15V, and –10V to –15V, respectively.
5 Voltage Reference
The ADS1259EVM has three options for supplying a reference voltage to the ADS1259. There are two
options for an external reference and one option with the internal ADS1259 reference.
Switch S1 selects an external reference from an external reference voltage using pins J8.18 (REF–) and
J8.20 (REF+) from the analog interface header or the REF5025 reference (U11). With the switch set to the
left, switch S1 selects the external reference voltage that is connected to the header of J8. With the switch
set to the right, S1 selects the onboard reference from the REF5025.
Figure 5 shows switch S1 as it
appears on the EVM.
Figure 5. Switch S1
Alternately, the ADS1259 also has an internal reference that can be used. The REFOUT pin allows for
measurement of this reference as well as a source that can be used to drive other functions, such as a
measurement bridge or the output common mode of the PGA280. If the internal reference is selected, set
switch S1 to the analog interface header, and leave the reference inputs at J8 unconnected.
8 ADS1259EVM, ADS1259EVM-PDK SBAU163A – March 2010 – Revised April 2010
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