SBAU394B April   2022  – August 2025

 

  1.   1
  2.   Description
  3.   Features
  4.   4
  5. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
    5. 1.5 Quick Start Guide
  6. 2Hardware
    1. 2.1 ADC Analog Input Signal Path
    2. 2.2 ADC Connections and Decoupling
    3. 2.3 Power Supplies
    4. 2.4 ADC Input Clock (CLK) Options
    5. 2.5 Digital-to-Analog Converter (DAC)
    6. 2.6 Digital Interface
    7. 2.7 Connection to the PHI
    8. 2.8 Digital Header
  7. 3Software Installation
  8. 4EVM Configuration and GUI Operation
    1. 4.1 EVM Configuration
    2. 4.2 GUI Operation
      1. 4.2.1 EVM GUI Global Settings for ADC Control
      2. 4.2.2 Register Map Configuration Tool
      3. 4.2.3 Time Domain Display Tool
      4. 4.2.4 Spectral Analysis Tool
      5. 4.2.5 Histogram Tool
      6. 4.2.6 DAC Configuration Tool
  9. 5Hardware Design Files
    1. 5.1 Schematics
    2. 5.2 PCB Layout
    3. 5.3 Bill of Materials
  10. 6Additional Information
    1. 6.1 Trademarks
  11. 7References
  12. 8Revision History

2.5 Digital-to-Analog Converter (DAC)

The ADS1285EVM-PDK includes a DAC1282, which is a fully integrated digital-to-analog converter (DAC) that provides a low-distortion, digital-synthesized voltage output designed for testing seismic equipment and the ADS128x family of devices. For more information, see the DAC1282 Low Distortion Digital-to-Analog Converter for Seismic Data Sheet. The DAC1282 can be used in combination with the GUI to directly supply an input voltage for testing and performance purposes. For more information on configuring the inputs to use the DAC1282, see Section 2.1.

The DAC output frequency in Sine mode is programmable from 0.5Hz to 250Hz and the magnitude is scaled by both analog and digital control. The analog gain is adjustable in 6-dB steps and the digital gain in 0.5-dB steps. The analog gain settings match those of the ADS1285 for high-resolution testing at all gains. Control the DAC1282 settings using the DAC Configuration page of the GUI as explained in Section 4.2.6.

The DAC1282 uses AVSS+5V and DVDD for the power supplies and shares the same reference as the ADS1285. This configuration minimizes potential errors from using separate references between the devices. However, most of the DAC1282 documentation is in reference to a 5V supply while the ADS1285EVM-PDK uses a 4.096V reference by default. As a result, the DAC output amplitude is scaled in reference to the 4.096V reference through the following equation:

Equation 1. V o u t _ p e a k = V F S R _ p e a k × 10 G D A C _ D i g ( d B ) 20

where:

  • Vout_peak = Output amplitude of the DAC in Sine mode
  • VFSR_peak = Positive peak of the full-scale range calculation, which depends on voltage reference
  • GDAC_Dig(dB) = Digital gain of the DAC determined by the SINEG register

This equation and scaling is automatically calculated in the ADS1285EVM-PDK GUI; see Section 4.2.6.