SLAAEI7 December   2023 MSPM0G3507

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Technology
    1. 2.1 Analog Peripherals in the MSPM0
    2. 2.2 Instrumentation Amplifier - INA350
    3. 2.3 Voltage Reference - REF2925
    4. 2.4 Low-Dropout Regulator - TPS7B6933-Q1
  6. 3Signal Chain
  7. 4Results
    1. 4.1 Influence of the OPA Chopping Mode
    2. 4.2 Oversampling and Hardware Averaging
    3. 4.3 Effect of Sampling Rate on Effective Resolution
    4. 4.4 Influence of the Amplification Factor
  8. 5Summary
  9. 6References

4 Results

When considering the whole signal chain, multiple factors influence the achievable resolution. These factors include the sampling rate used to capture the signal, the reference voltage used, the chopping method used for the amplifiers, and the amplification factor of the operational amplifiers.

The results consider the effective resolution of the whole signal chain. In the use case of pressure sensors, the pressure changes relatively slowly, therefore, to detect changes in the pressure the sampling speed can be limited. The analysis of the results is limited only to frequencies below 10 kHz and does not account for the factor of harmonics and other distortions in higher frequency signals. Equation 2 and Equation 3 were used to calculate the effective resolution of the signal chain.

Equation 2. E N O B s   D C   I n p u t   =   μ σ   w i t h   μ   =   a v e r a g e   A D C   o u t p u t   c o d e   a n d   σ   =   ∑ ( x - µ ) 2 n   i n   L S B s
Equation 3. N F   b i t s   f o r   D C   i n p u t   =   µ N p p   w i t h   N p p   b e i n g   t h e   p e a k   t o   p e a k   n o i s e   i n   L S B s

The measurements are carried out by sampling a continuous signal for a fixed number of samples. The level of this continuous signal is selected so that the input to the ADC is always close to the full scale of the VREF.