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

2.1.2 Differential Voltage Inputs Channels

Figure 2-2 shows the schematic for one input channel that, by default, measures differential voltage signals from -10V to +10V. This voltage is measured directly by the ADS125H18 without the need for external attenuation. Table 2-6 describes the function of each component in the differential voltage input channel schematic. Additionally, Table 2-6 references component designators specifically from Figure 2-2; however, the information in the table generally applies to all differential voltage input channels.

ADS125H18EVM-PDK Differential Voltage Input ChannelFigure 2-2 Differential Voltage Input Channel
Table 2-3 Important Components (Differential Voltage Input Channels)

COMPONENT

FUNCTION

Terminal block (17)

Apply one differential voltage signal per terminal block

TVS diode (U19 and U20)

  • 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 (R51)

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

The shunt is not installed by default on this channel

Zener diodes (D16 and D18)

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

The Zener diodes are not installed by default on this channel

0Ω resistor

(R54)

Placeholder for a PTC fuse that must only be installed when the user reconfigures this channel for differential current measurements

Filter components (R48, R49, C41, C47, and C48)

Provides additional input filtering if desired

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

Figure 2-2 shows that the default voltage input channel configuration is differential-ended. As a result, the EVM supports measurement of voltage 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 voltage input channel can also be configured as a differential current input channel by installing the PCB-mounted shunt and Zener diodes, as well as replacing the 0Ω resistor with a PTC fuse.