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

4.2.1 ADC Capture Settings and Sequencer Configuration

Figure 4-3 shows how the Pages control in the upper-left corner allows access to the other pages in the GUI. Navigate to any of the GUI pages using these controls. Figure 4-3 also shows the ADC Capture page. Use this page to easily configure the most important ADC settings, including the General Configuration and Step Configuration parameters, the sequencer mode, and the number of samples or sequences to capture.

ADS125H18EVM-PDK ADS125H18 EVM GUI ADC Capture Page - General ConfigurationFigure 4-3 ADS125H18 EVM GUI ADC Capture Page - General Configuration

The General Configuration tab allows the user to set certain parameters that are used for all steps, including the speed mode, the internal reference voltage, the state of the reference buffer, and the Test DAC range. Additionally, the user can enter the External Reference Voltage if applicable. The ADC Capture page also reports the device attenuation by reading the ADC DEVICE_ID register. Finally, the “Ready” box indicates if the GUI is ready to communicate to the ADC (in blue) or if the GUI is busy communicating with the ADC (in orange).

The default option in the sequencer mode dropdown in Figure 4-3 allows the user to capture n conversions of a single step, where n is the number entered in the box in the lower left of the GUI. Alternatively, enable the sequencer to capture n complete sequences of all enabled steps.

Figure 4-4 shows the Step Configuration tab. Use these controls to configure the settings for each individual step. When the sequencer is disabled, only Step 0 is shown.

ADS125H18EVM-PDK ADS125H18 EVM GUI ADC Capture Page - Step ConfigurationFigure 4-4 ADS125H18 EVM GUI ADC Capture Page - Step Configuration

Table 4-1 explains in more detail each field shown in Figure 4-4:

Table 4-1 Understanding the Step Configuration Page Parameters

ITEM #

PARAMETER

DESCRIPTION

1

REF_SEL

Select the reference voltage source to be used with this step

2

AIN

Select the measurement channel for this step

3

SYS_MON

Select the system monitor option to be measured in this step

NOTE: The system monitor takes precedence over the AIN selection (see #2 above), and also uses the internal reference regardless of the selection in REF_SEL

4

FLTR_OSR

Select the OSR for this step

NOTE: The data rate corresponding to this OSR is shown on the right (see #10 below)

5

FLTR_MODE

Select the filter mode for this step

6

Delay in tmods

Enter the programmable delay used for this step

NOTE: The delay value is measured in modulator clock periods (tMOD), where the modulator clock is selected by the SPEED_MODE field on the General Configuration tab

7

EVM I/V SWITCH

Select the state of the I/V switch on the EVM for this step

NOTE: This is a feature of the EVM, not the ADC. These switches are only installed on the EVM on differential channels AIN2/AIN3 and AIN4/AIN5, so this selection only affects those channels

8

TDAC_SEL

Select the location where the Test DAC voltage is output to in this step

9

TDAC_VAL

Select the Test DAC voltage to be used for this step

NOTE: Enter a value between 0 and 31, which is calculated in volts in the "Test DAC (V)" field on the right (see #13 below)

10

Data Rate (SPS)

Data rate relative to the selected OSR (see #4 above) and the SPEED_MODE, assuming the internal oscillator is used

NOTE: Select the SPEED_MODE on the General Configuration tab

11

Latency (μs)

Calculates the first conversion latency in microseconds

NOTE: First conversion latency includes the complete digital filter settling resulting from the FLTR_OSR and FLTR_MODE fields, as well as any additional delay entered in the Delay in Tmods field, if applicable

12

Full Scale Voltage

Calculates the full-scale voltage (FSV) for this step, where FSV = Reference Voltage * Attenuation Factor

NOTE: Set the reference voltage on the General Configuration tab. The GUI determines the Attenuation Factor by reading the DEVICE_ID register

13

Test DAC (V)

Calculates the TDAC voltage in volts, where TDAC = TDAC_VAL * TDAC_RANGE

NOTE: Set TDAC_VAL on the Step Configuration tab and set TDAC_RANGE on the General Configuration tab

Enable the ADC sequencer by selecting "Sequencer enabled: continuous mode" from the SEQ_MODE dropdown on the General Configuration tab. Multiple step options appear after selecting this configuration. Additionally, the Capture parameter changes from "Samples" to "Sequences". As a result, the GUI captures and displays the data for the desired number of sequences defined by the user. Figure 4-5 shows how the GUI changes after enabling the sequencer.

ADS125H18EVM-PDK ADS125H18 EVM GUI ADC Capture Page - Enable SequencerFigure 4-5 ADS125H18 EVM GUI ADC Capture Page - Enable Sequencer

After enabling the sequencer, Figure 4-6 shows how clicking on each individual step opens up a new step tab. Clicking on the same step again closes that step tab. This is true for all steps except Step 0, which cannot be disabled.

ADS125H18EVM-PDK ADS125H18 EVM GUI ADC Capture Page - Enabling Multiple Sequence StepsFigure 4-6 ADS125H18 EVM GUI ADC Capture Page - Enabling Multiple Sequence Steps.

Configure each enabled step as shown in Figure 4-4 and described in Table 4-1. Enabling the sequencer also enables the NUM_CONV control on each step page. The NUM_CONV control allows the user to select a specific number of consecutive conversions on that step, instead of taking a single conversion and then immediately switching to the next step. However, the GUI limits the number of sequences to one if the user selects NUM_CONV > 1 on any step page. Figure 4-7 shows this behavior, including a note in the GUI that explains how this limitation is a result of the GUI and not the ADC.

ADS125H18EVM-PDK ADS125H18 EVM GUI ADC Capture Page - Number of Conversions FieldFigure 4-7 ADS125H18 EVM GUI ADC Capture Page - Number of Conversions Field.