SBAU433B November   2025  – April 2026 ADS125H18

 

  1.   1
  2.   Description
  3.   Get Started
  4.   Features
  5.   Applications
  6.   6
  7. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specifications
    4. 1.4 Device Information
  8. 2Hardware
    1. 2.1 Analog Inputs
      1. 2.1.1 Differential Current Input Channels
      2. 2.1.2 Differential Voltage Inputs Channels
      3. 2.1.3 Combined Differential Current and Voltage Input Channels
      4. 2.1.4 Single-Ended Current Input Channels
    2. 2.2 ADC Connections and Decoupling
    3. 2.3 Digital Interface
    4. 2.4 Power Supplies
    5. 2.5 Voltage Reference
    6. 2.6 Clocking
    7. 2.7 Using the ADS125H18 EVM With an External Controller
  9. 3Software
    1. 3.1 Software Description
    2. 3.2 ADS125H18 GUI Installation
  10. 4Implementation Results
    1. 4.1 Hardware Connections
    2. 4.2 GUI Operation
      1. 4.2.1 ADC Capture Settings and Sequencer Configuration
      2. 4.2.2 Time-Domain Display
      3. 4.2.3 Frequency-Domain Display
      4. 4.2.4 Histogram Display
      5. 4.2.5 EVM Register Settings
  11. 5Hardware Design Files
    1. 5.1 Schematics
    2. 5.2 PCB Layouts
    3. 5.3 Bill of Materials (BOM)
  12. 6Additional Information
    1. 6.1 Trademarks
  13. 7Revision History

2.1.1 Differential Current Input Channels

Figure 2-1 shows the schematic for one input channel that, by default, measures differential current signals from -20mA to +20mA. This current flows through a PCB-mounted shunt that is converted to a voltage and then measured by the ADS125H18.Table 2-6 describes the function of each component in the differential current input channel schematic. Additionally, Table 2-6 references component designators specifically from Figure 2-1; however, the information in the table generally applies to all differential current input channels.

ADS125H18EVM-PDK Differential Current Input ChannelFigure 2-1 Differential Current Input Channel
Table 2-2 Important Components (Differential Current Input Channels)

COMPONENT

FUNCTION

Terminal block (J1)

Apply one differential current signal per terminal block

TVS diode

(U2 and U3)

  • Protection device that limits transient voltage into the ADC

  • The recommended component (TVS3301) offers bidirectional voltage suppression at a typical breakdown voltage of 37.5V

The TVS diodes are not installed by default on this channel

Shunt (R14)

Converts the current signal to a voltage to be read by the ADC

Zener diodes (D5 and D6)

Protection device that limits the current through the shunt in case of a sustained positive or negative overvoltage event

PTC fuse (F1)

Protection device whose resistance increases with temperature, thereby increasing the total circuit resistance. This increased resistance limits the current through the shunt in the case of a sustained overvoltage event

Filter components (R18, R19, C15, C16, and C24)

Provides additional input filtering if desired

The capacitors are not installed by default on this channel. The installed resistors are 0Ω

Figure 2-1 shows that the default current input channel configuration is differential-ended. As a result, the EVM supports measurement of current inputs that are at different common-mode voltages. However, verify that the absolute voltage on any input pin does not exceed the values specified in the ADS125H18 datasheet.

A differential current input channel can also be configured as a differential voltage input channel by removing the PCB-mounted shunt and Zener diodes, as well as replacing the PTC fuse with a 0Ω resistor.