SBAU413A october   2022  – may 2023

 

  1.   Abstract
  2.   Trademarks
  3. 1EVM Overview
    1. 1.1 ADS131B26Q1EVM-PDK Features
    2. 1.2 ADS131B26Q1EVM-PDK Quick-Start Guide
  4. 2Analog Interface
    1. 2.1 Terminal Blocks and Test Points
    2. 2.2 ADC1A and ADC1B
    3. 2.3 ADC2A and ADC2B
    4. 2.4 ADC3A and ADC3B
  5. 3Digital Interface
    1. 3.1 Connection to the PHI Controller
    2. 3.2 Digital Header
    3. 3.3 Clock Options
  6. 4Power Supplies
    1. 4.1 DC/DC Converter Circuit
    2. 4.2 ADC Power Supplies
    3. 4.3 Power Supply and Voltage Reference Decoupling
  7. 5ADS131B26Q1EVM-PDK Initial Setup
    1. 5.1 Default Jumper Settings
    2. 5.2 EVM Graphical User Interface (GUI) Software Installation
  8. 6ADS131B26Q1EVM-PDK Software Reference
    1. 6.1 Global Settings for ADC Control
    2. 6.2 Register Map Configuration
      1. 6.2.1 Register Map Basics
      2. 6.2.2 ADC1A, ADC3A and ADC1B, ADC3B Configuration
      3. 6.2.3 ADC2A and ADC2B Configuration
    3. 6.3 Analysis Tools
      1. 6.3.1 Time Domain Display
      2. 6.3.2 Spectral Analysis Tool
      3. 6.3.3 Histogram Analysis
      4. 6.3.4 Sequencer Analysis
  9. 7ADS131B26Q1EVM-PDK Bill of Materials, PCB Layout, and Schematics
    1. 7.1 Bill of Materials (BOM)
    2. 7.2 PCB Layout
    3. 7.3 Schematics
  10. 8Revision History

6.3.2 Spectral Analysis Tool

The Spectral Analysis tool is intended to evaluate the dynamic performance of ADC1A, ADC3A, ADC1B, and ADC3B. This tool analyzes the AC characteristics of the ADC and input signal source.

The Data Capture Configuration panel on the left side of the window allows the user to independently specify the oversampling ratio (OSR) used by ADC1A, ADC3A and ADC1B, ADC3B by configuring OSR13A and OSR13B, respectively. Even though the resulting data rates can differ, the resulting fast-fourier transform (FFT) always plots from DC to one-half the data rate for each channel. Therefore, one channel FFT plot can easily occupy less of the x-axis than the other.

The Measurements summary table above the FFT plot is updated based on the Display Channel drop-down menu selection. The calculated specifications include SNR, THD, SFDR, SINAD, and ENOB. The GUI also identifies the frequency and signal power of the fundamental component of the input signal, and the frequency and signal power of the largest spur component.

Under the Configuration section, select the number of harmonics used for distortion calculations (default = 9 harmonics) and specify the windowing function required to mitigate the effects of non-coherent sampling. The 7-Term Blackman-Harris window is the default option and has sufficient dynamic range to resolve the frequency components of a 24-bit ADC. The None option corresponds to not using a window (or using a rectangular window) and is not recommended. Both the calculated specifications and the FFT plot can be displayed in dBc or dBFS units by toggling the radio buttons beneath the Display Channel drop-down menu.

Figure 6-6 shows the Spectral Analysis Tool window. Initiate a data capture by specifying the number of samples and clicking the Capture button at the bottom of the Data Capture Configuration panel. In the example below, ADC3A is configured for 64 kSPS (OSR13A = 64) and is measuring a 2-kHz single-ended sine wave, producing a –6.26 dBFS input signal. The resulting FFT is plotted from DC to 32 kHz. For fully-differential inputs, restrict the input signal amplitude to –0.5 dBFS maximum (approximately 95% of full-scale) to avoid saturating the ADC channels and introducing unwanted distortion terms into the signal. ADC3B is configured to measure an internal short to AGNDB at 32 kSPS (OSR13B = 128). As a result, the noise floor of ADC13B is only plotted from DC to 16 kHz.

GUID-20220922-SS0I-RXQP-QH8T-BC6SKJS3NCQN-low.svg Figure 6-6 Spectral Analysis Tool