Voltage Reference - Texas Instruments ADS1258EVM-PDK User Manual

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3.5 Voltage Reference

The ADS1258EVM requires a precision reference voltage to accurately convert the analog inputs to digital
outputs. Figure 3-6 shows the EVM voltage reference circuitry.
AVDD
C4
10uF
R5
120k
TP1
GND
The EVM includes two options to provide a reference voltage to the ADC. The first option is an installed
component: the low-noise, low-drift, buffered-output REF6025. This discrete voltage reference outputs a voltage
of 2.5 V to the ADC reference pins (REFOUT and ground). Additionally, the REF6025 output voltage is also
connected to the J3 terminal block as REFOUT.
The second voltage reference option on the EVM is to use an external voltage source. An external component
can be useful if a reference voltage other than 2.5 V is required. Configure the EVM for an external voltage
reference by moving the 0-Ω resistor at R4 to R2. Then connect EXT_VREFP on J3 to the external reference
output voltage, and connect the external reference ground to the EVM ground. REFOUT on J3 is shorted
to EXT_VREFP to make sure that the reference voltage can still be used to bias external circuitry. See the
ADS1258 data sheet for information about the allowable voltage range on the VREFx pins.
SBAU126E – MAY 2007 – REVISED JUNE 2023
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U1
1
VIN OUT_S
2
EN OUT_F
3
SS GND_F
4
FILT GND_S
C5
REF6025IDGKR
1µF
Figure 3-6. ADS1258EVM Voltage Reference Circuit
Copyright © 2023 Texas Instruments Incorporated
J3
R2
0
5
R4
6
0
7
C3
22µF
8
R6
0.047
GND
ADS1258EVM-PDK Evaluation Module
Analog Interface
R1
AINCOM
1.00k
JP2
Short AINCOM
DNP
C1
to REFOUT
470pF
REFOUT
GND
ACOM
9