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

5.3.1 (R1+R2)/R2 calibration

For more information, see structure1 in Figure 5-4. ADC channel 12 and ADC channel 7 is used to test the voltage divided by R1 and R2. You will also increase the DAC output to make OPA1 output closed to the ADC full range, to increase the accuracy. In order to reduce the resistance influence of GPIO trace, choose to test the voltage at OPA0 internal ADC trace directly, instead of the GPIO output (PA22/A4). Equation 6 is the calibration equation based on ADC detected numbers:

Equation 6. R1+R2R2=NA12NA12-NA7

In this current detection demo, as the VDD=1.8 V and the selected internal reference is 1.4 V. In order to get a high changeable OPA1 voltage output range with GAIN32 and GAIN16 setting paired with DAC change, we choose to make (R1+R2)/R1 = 8.