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

7.1 Calibration Test Result

After you enable the “DEBUG”, you can output the calibration data through UART1. This data can help to evaluate the calibration error. The data shown in this part are all from one MSPM0L1306 with 1.8 V supply and comes from a 12-bit ADC with 1.4 V internal reference under 25°C.

Figure 7-1 shows the test data of (R1+R2)/R1. You can see that the value fluctuation is ±0.13%.

GUID-AD54054B-D73D-4945-B288-6AFE1F8008E3-low.png Figure 7-1 Tested (R1+R2)/R1 Under 25C

Figure 7-2 shows the voltage output offset with different gain. All of them are below than 0.7 mV.

GUID-AAB33118-FF02-4F84-8F6E-F839B0AA2A0B-low.png Figure 7-2 Tested OPA1 Offset Under 25°C

Figure 7-3 shows the test data of (R3+R4)/R3. You can see that the value fluctuation under GAIN32 is ±0.11%. For GAIN16, it is ±0.13%.

GUID-7B63EF22-F001-4A57-8CA3-7C969B40FF32-low.png Figure 7-3 Tested (R3+R4)/R3 Under 25°C

To evaluate the calibration accuracy, compare the calculated Vref through the Equation 2 and the tested Vref through ADC channel 13, when the current is 0. Pay attention that the tested data is the raw data from 12-Bit ADC with 1.4 V reference. The Vref is about 0.7 V, close to ½ ADC reference.

You can see that the tested Vref almost only have 1 or 2 ADC count change in two GAIN settings. If you treat the tested Vref as the accurate value for the GAIN32 setting, the max calculated Vref error is about 0.2%. For GAIN16 setting, it is about 0.15%.

As seen from these results, you can say that the self-calibration structure is very stable and has a very high accuracy.

GUID-909F7618-92D1-4055-A19E-015A8064B916-low.png Figure 7-4 Tested and Calculated Vref Under 25°C