SBAU394A April   2022  – September 2022

 

  1.   ADS1285 Evaluation Module
  2.   Trademarks
  3. 1 EVM Overview
    1. 1.1 ADS1285EVM-PDK Kit
  4. 2 ADS1285EVM-PDK Quick-Start Guide
  5. 3 EVM Analog Interface
    1. 3.1 ADC Analog Input Signal Path
    2. 3.2 ADC Input Clock (CLK) Options
  6. 4 Digital Interface
    1. 4.1 Connection to the PHI
    2. 4.2 Digital Header
  7. 5 Power Supplies
  8. 6 Digital-to-Analog Converter
  9. 7 ADS1285EVM-PDK Initial Setup
    1. 7.1 Default Jumper Settings
    2. 7.2 EVM Graphical User Interface (GUI) Software Installation
  10. 8 ADS1285EVM-PDK Software Reference
    1. 8.1 EVM GUI Global Settings for ADC Control
    2. 8.2 Register Map Configuration Tool
    3. 8.3 Time Domain Display Tool
    4. 8.4 Spectral Analysis Tool
    5. 8.5 Histogram Tool
    6. 8.6 DAC Configuration Tool
  11. 9 ADS1285EVM-PDK Bill of Materials, PCB Layout, and Schematics
    1. 9.1 Bill of Materials
    2. 9.2 PCB Layout
    3. 9.3 Schematics
  12. 10References
  13. 11Revision History

6 Digital-to-Analog Converter

The ADS1282EVM-PDK contains 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; see the DAC1282 data sheet for more information. 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 3.1.

If using the DAC in Sine mode, the output frequency is programmable from 0.5 Hz to 250 Hz 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 ADS1282 for testing at all gains with high resolution. Controlling the settings of the DAC1282 can be done on the DAC Configuration page of the GUI as explained in Section 8.6.

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 5-V supply where the ADS1285EVM-PDK uses a 4.096-V reference by default. As a result, the DAC output amplitude is scaled in reference to the 4.096-V reference through the following equation:

Equation 1. Vout_peak=VFSR_peak∙10GDAC_Dig(dB)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 8.6.