Texas Instruments ADS1x48EVM User Manual page 18

ADS1x48EVM Overview
between the analog input and reference voltages. As a result, the absolute IDAC accuracy is less critical and
the system performance improves. However, choose the IDAC current magnitude and the total circuit impedance
to ensure that the ADC IDAC compliance voltage is met. For additional information regarding ratiometric
references, RTD measurement circuits using precision ADCs, and important specifications including compliance
voltage, see the A Basic Guide to RTD Measurements application
R11 is chosen to be 4.02 kΩ in order to accommodate high-impedance RTDs at high temperature ranges. For
example, a Pt1000 at 850°C has a typical impedance of approximately 3.9 kΩ. If a smaller measurement range
is required, replace R11 with a different resistor in an 0805 package or remove R11 and use an external resistor
connected between REFP1 and REFN1 on J6. Choose a high accuracy, low-drift resistor to ensure best system
performance.
All common RTD configurations can be measured with the ADS1x48EVM, including:
• 2-wire RTD using a low-side R
• 2-wire RTD using a high-side R
• 3-wire RTD using one IDAC and a low-side R
• 3-wire RTD using one IDAC and a high-side R
• 3-wire RTD using two IDACs and a low-side R
• 3-wire RTD using two IDACs and a high-side R
• 4-wire RTD using a low-side R
• 4-wire RTD using a high-side R
The ADS1x48EVM accomplishes maximum flexibility using jumpers JP3, JP4, JP5, and JP6 (see
in conjunction with different analog inputs and IDAC routing. The following subsections detail the appropriate
connections and settings to enable each RTD configuration using the ADS1x48EVM. Each subsection contains
a connection diagram where the red lines indicate how current flows in the circuit. Moreover, the red text
indicates which jumpers are populated and which current sources are biasing the RTD, and the blue text
indicates the measurement channels. This information is summarized in
18 ADS1x48EVM Evaluation Module
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report.
Section 3.5.3.9.
SBAU378A – SEPTEMBER 2021 – REVISED JANUARY 2022
www.ti.com
Figure 3-12)
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