SLAA828B March   2018  – August 2021 MSP430FR2000 , MSP430FR2032 , MSP430FR2033 , MSP430FR2100 , MSP430FR2110 , MSP430FR2111 , MSP430FR2310 , MSP430FR2311 , MSP430FR2422 , MSP430FR2433 , MSP430FR2512 , MSP430FR2522 , MSP430FR2532 , MSP430FR2533 , MSP430FR2632 , MSP430FR2633 , MSP430FR4131 , MSP430FR4132 , MSP430FR4133

 

  1.   Trademarks
  2. 1Introduction
  3. 2ADC Low-Power Sampling Software Design
    1. 2.1 System Clock Source Selection
    2. 2.2 ADC Clock Source Selection
    3. 2.3 Initialization of Unused GPIO Pins
  4. 3ADC Error Correction and Experimental Testing
    1. 3.1 Error Correction
    2. 3.2 Accuracy Test
  5. 4Time-Division Multiplexing of the ADC to Achieve Additional Channel Acquisition
  6. 5Summary
  7. 6References
  8. 7Revision History

3.1 Error Correction

The use of on-chip ADC measurement of battery voltage, the error comes mainly from two aspects: ADC measurement error and 1.5-V reference voltage error. The data sheet shows calibration formulas for the measurement error of ADC and the error of 1.5-V reference voltage respectively.

However, the calibration factor used for the calibration of the 1.5-V reference is used only when 1.5 V used as the ADC reference. This calibration factor no longer applies when 1.5 V is used as an ADC input channel. Because 1.5 V is used as a reference voltage, it passes through a Reference Buffer, which is not available on the ADC input channel. In this case, calibrate only the ADC error.

Equation 3 shows the formula to calibrate the ADC.

Equation 3. GUID-221509AA-EE3C-45D3-B91F-F2A7B04C506D-low.gif

where

  • ADCcalibrated = calibrated value
  • Factorgain = ADC gain calibration factor
  • ADCoffset = ADC offset calibration factor

Because different series of calibration coefficients have different memory addresses, see the device-specific data sheet for the addresses of Factorgain and ADCoffset.