SBAA487 January   2021 ADS8664 , ADS8668 , ADS8674 , ADS8678 , ADS8684 , ADS8684A , ADS8686S , ADS8688 , ADS8688A , ADS8694 , ADS8698

 

  1.   Trademarks
  2. 1Introduction
  3. 2Phase Delay and Non-Simultaneous Sampling
  4. 3Averaging with Sequencer and Burst Sequencer mode
    1. 3.1 Averaging with Sequencer
    2. 3.2 Averaging with Burst Sequencer
  5. 4Verification and Measured Result
    1. 4.1 Phase Delay Measurement
      1. 4.1.1 Measured Phase Delay without Averaging – 50Hz Sinusoidal Fundamental Signal
      2. 4.1.2 Measured Phase Delay with Averaging – 50Hz sinusoidal fundamental signal
      3. 4.1.3 Comparison
    2. 4.2 AC Performance
  6. 5Summary
  7. 6References

4.2 AC Performance

The Phase Analysis integrated in ADS8686SEVM GUI does not have an ability to calculate and show the AC performance including signal-to-noise ratio (SNR) and total harmonic distortion (THD) directly since it is a real-time running software for phase analysis. However, the sample data for each channel can be saved to a .csv file by selecting Load Data to File from the menu Tools -> Data Log in Time Domain. The data file can be imported to Analog Engineer Calculator tool to get SNR and THD. Table 4-3 shows measured results with averaged sample data.

This test shows that the SNR on the averaged channels is better than the reference channel as expected because the noise is reduced by averaging technique. The THD is still maintained in the reasonable range.

Table 4-3 Measured AC Performance with Averaged Samples
Channel SNR (dB) THD (dB) Sample Data
AIN0A 92.24 -104.01 Averaged
AIN1A 92.23 -104.14 Averaged
AIN2A 92.18 -104.19 Averaged
AIN3A 92.11 -104.12 Averaged
AIN4A 91.92 -103.93 Averaged
AIN5A 91.75 -103.67 Averaged
AIN6A 91.44 -103.80 Averaged
AIN7A 90.76 -109.23 No Average on Reference CH

Test condition and procedure

  1. Apply - 0.5dBFS, 1kHz sinusoidal signal to all input channels on ADS8686SEVM.
  2. Set Load Data to File from the menu Tools -> Data Log in Time Domain page in the GUI.
  3. Select Burst Mode and Sample Averaging in Phase Analysis in the EVM GUI.
  4. Capture the data with proper number samples. The sample data can be found in the .csv file.
  5. Use the Analog Engineer Calculator tool to load the averaged data and check AC performance.