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

7.2.2 Test Under 0°C

Figure 7-6 shows the current test pattern (left) and the detection error (tight) under 0°C. However, the GAIN factor is gotten at 25°C. That is why you can find a 4 mA offset when the current is 0. After you transmit this 4 mA current into the output voltage shift and compare it with Vref, you can evaluate the GAIN factor shift is about 0.4% (About 2.56 mV output voltage shift with Vref=700 mV).

Under this condition, you can find that this solution can control the error within 22 mA in the range of ±2000 mA. The error percentage is below than ±1.1% at ±2000 mA.

GUID-27121E51-3EB5-453E-905C-23ABC9B2EAA5-low.png Figure 7-6 Current Test Under 0°C With 25°C Calibration

See what happens when you do GAIN factor calibration under 0°C. You can find that offset current is reduced to 3 mA. However, the error reaches to 25 mA in the range of ±2000 mA. The error is below than ±1.3% at ±2000 mA.

GUID-0659A863-0CA2-4C75-A52C-965F9501AA13-low.png Figure 7-7 Current Test Under 0°C With 0°C Calibration

You will see that the current detection error is increased when the GAIN factor is gotten under 0°C. Considering the GAIN factor shift, you would assume the increase error lies on the shunter resistor value shift.