SBAU315B July   2018  – March 2025 ADS9224R , ADS9234R

 

  1.   1
  2.   ADS9224REVM-PDK
  3.   Trademarks
  4. 1Overview
    1. 1.1 ADS9224REVM-PDK Features
    2. 1.2 ADS9224REVM Features
  5. 2Analog Interface
    1. 2.1 Connectors for Signal Source
    2. 2.2 ADC Differential Input Signal Driver
      1. 2.2.1 Input Signal Path
    3. 2.3 ADS9224R Internal Reference
  6. 3Digital Interfaces
    1. 3.1 multiSPI for ADC Digital IO
  7. 4Power Supplies
  8. 5Setup
    1. 5.1 Default Jumper Settings
    2. 5.2 EVM Graphical User Interface (GUI) Software Installation
  9. 6Operation
    1. 6.1 EVM GUI Global Settings for ADC Control
    2. 6.2 Register Map Configuration Tool
    3. 6.3 Time Domain Display Tool
    4. 6.4 Spectral Analysis Tool
    5. 6.5 Histogram Tool
  10. 7ADS9224REVM Bill of Materials, PCB Layout, and Schematics
    1. 7.1 Bill of Materials
    2. 7.2 PCB Layout
    3. 7.3 Schematics
  11. 8Revision History

6.4 Spectral Analysis Tool

The spectral analysis tool evaluates the dynamic performance (SNR, THD, SFDR, SINAD, and ENOB) of the ADS9224R SAR ADC. Evaluation is done through single-tone sinusoidal signal FFT analysis using the 7-term Blackman-Harris window setting. The window setting of None can be used to search for noise spurs over frequency in dc inputs.

For dynamic performance evaluation, the external differential source must have better specifications than the ADC. The measured system performance must not be limited by the performance of the signal source. Therefore, the external reference source must meet the source requirements mentioned in Table 6-1.

Table 6-1 External Source Requirements for Evaluation of the ADS9224R
Specification Description Specification Value
Signal frequency Less than fS / 2
External source type Balanced differential
External source common-mode voltage 0 V or floating
Source differential signal
(VPP amplitude for –0.5 dBFS)		 ±3.875 VP OR 7.75 VPP
Maximum noise 20 µVRMS
Minimum SNR 103.2 dB
Maximum THD –120 dB

For 2-kHz SNR and ENOB evaluation at a maximum throughput of 3 MSPS, the number of samples must be a minimum of 65536.

Spectral Analysis ToolFigure 6-6 Spectral Analysis Tool

Finally, the FFT tool includes windowing options that are required to mitigate the effects of noncoherent sampling (a discussion that is beyond the scope of this document). The 7-Term Blackman Harris window is the default option and has sufficient dynamic range to resolve the frequency components of up to a 24-bit ADC. The None option corresponds to not using a window (or using a rectangular window) and is not recommended.