SLAAEE6 October   2023 MSPM0L1306 , MSPM0L1306

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Hardware Introduction
  6. 3Software Introduction
  7. 4Gauge GUI Introduction
  8. 5Current Detection and Calibration Method
    1. 5.1 MSPM0 OPA Introduction
      1. 5.1.1 OPA input and output limitation
      2. 5.1.2 OPA Accuracy Influence
    2. 5.2 Current Detection Method
    3. 5.3 Current Calibration Method
      1. 5.3.1 (R1+R2)/R2 calibration
      2. 5.3.2 OPA1 Voffset calibration
      3. 5.3.3 R3/(R4+R3) calibration
      4. 5.3.4 Vref calibration
  9. 6Solution Evaluation Steps
    1. 6.1 Step1: Hardware Preparation
    2. 6.2 Step2: Evaluation
  10. 7MSPM0 Gauge Solution Test Results
    1. 7.1 Calibration Test Result
    2. 7.2 Current Detection Result
      1. 7.2.1 Test Under 25°C
      2. 7.2.2 Test Under 0°C
      3. 7.2.3 Test Under 50°C
      4. 7.2.4 Conclusion
    3. 7.3 Current Consumption Test
  11. 8Solution Summery and Improvement Direction
    1. 8.1 Shunter Resistor
    2. 8.2 ADC and its Reference
    3. 8.3 Runtime Calibration

5.3.3 R3/(R4+R3) calibration

For more information, see structure 3 in Figure 5-4. The structure of R3/(R4+R3) calibration is the same with the final current test. The difference lies on that the DAC output is increased to make the OPA1 output to be closed to ADC full range in order to get higher accuracy. Instead of testing the voltage at PA18, use the calibrated (R1+R2)/R1 value and the detection result at A12 to calculate the PA18 voltage. This can help increase the resolution and reduce the DAC noise, compared with directly connecting OPA0 to PSEL MUX. For this demo, you also need to do two different R3/(R4+R3) calibration. Equation 8 shows the equation based on ADC detected numbers.

Equation 8. R 3 R 4 + R 3 = R 1 R 1 + R 2 * N A 12 N A 13 - N V o f f s e t