SLAAEO8 October   2024 MSPM0C1103 , MSPM0C1103-Q1 , MSPM0C1104 , MSPM0C1104-Q1 , MSPM0G1105 , MSPM0G1106 , MSPM0G1107 , MSPM0G1505 , MSPM0G1506 , MSPM0G1507 , MSPM0G1519 , MSPM0G3105 , MSPM0G3105-Q1 , MSPM0G3106 , MSPM0G3106-Q1 , MSPM0G3107 , MSPM0G3107-Q1 , MSPM0G3505 , MSPM0G3505-Q1 , MSPM0G3506 , MSPM0G3506-Q1 , MSPM0G3507 , MSPM0G3507-Q1 , MSPM0G3519 , MSPM0L1105

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1ADC Introduction
    1. 1.1 SAR ADC Principle
    2. 1.2 ADC Parameters
      1. 1.2.1 Static Parameters
      2. 1.2.2 Dynamic Parameters
        1. 1.2.2.1 AC Parameters
        2. 1.2.2.2 DC Parameters
  5. 2ADC Noise Analysis
    1. 2.1 ADC Noise Classification
      1. 2.1.1 ADC Noise
      2. 2.1.2 Reference Noise
      3. 2.1.3 Power Supply Noise
      4. 2.1.4 ADC Input Noise
      5. 2.1.5 Clock Jitter
    2. 2.2 How to Reduce Noise
      1. 2.2.1 Reducing Input Noise Through RC Filtering
      2. 2.2.2 Layout Suggestions
      3. 2.2.3 Improving Signal-to-Noise Ratio
      4. 2.2.4 Choose a Suitable Reference Voltage Source
      5. 2.2.5 Software Methods for Reducing Noise
  6. 3ADC Oversampling
    1. 3.1 Sampling Rate
    2. 3.2 Extraction
    3. 3.3 Application Conditions
  7. 4ADC Application Based on MSPM0
    1. 4.1 ADC Configuration of MSPM0
    2. 4.2 ADC DC Test Based on MSPM0G3507 ADC EVM Board
      1. 4.2.1 Software/Hardware Configuration
        1. 4.2.1.1 Hardware
        2. 4.2.1.2 Software
      2. 4.2.2 Test Result
      3. 4.2.3 Result Analysis and Conclusion

4.2.3 Result Analysis and Conclusion

  • Analysis and conclusion

    The information can be found with the following test result:

  • Observe peak-peak value based on ttlDeltaSample value of different reference voltage without oversampling, except “external 2.5” is much lower, others have close peak-peak voltage. The peak to peak voltage is caused by spikes on the ADC input. As it is much larger than ADC internal noise and reference noise (also larger than the peak-peak value calculated by 6*standard deviation), they have similar results in different voltage refence and it cannot reflect the performance differences of different reference voltages;
  • Oversampling could effectively reduce input noise and improve ADC output SNR. The more samples oversampling collects, the larger SNR is. But it will also cause the decrease of valid sampling frequency.
  • By compare effective resolution of different reference voltage, we could get the conclusion about the reference performance with the same DC input:

    External VDD 3.3V > External 2.5V > Internal VDDA > Internal 2.5V > Internal 1.4V

    • The external reference generally has better performance than internal reference, while it means more cost and PCB area.
    • When "signal noise > quantization noise", a higher reference could result in higher resolution, where signal noise includes reference noise, thermal noise and other noises added in input signal.
    • When "signal noise < quantization noise", a lower reference means lower quantization noise, and it could result in higher resolution and better accuracy. And ADC LSB determines the upper limit of ADC accuracy.
  • Statement
  • The above test results only reflect the results on the MSPM0G3507 ADC EVM board. The actual ADC application performance of customers are closely related to the accuracy and layout of the external reference voltage. The above results are not guaranteed to be reproducible, and better results may also be achieved in actual ADC application situation;
  • The above results only reflect the ADC test results under DC input, and the effective resolution is not the same concept as ENOB, which is inconsistent with the AC parameters on the device-specifc data sheet;
  • When selecting a lower precision reference voltage source, or having a poor layout and wiring, the sampling accuracy of the external reference ADC may not be as good as the internal reference.