SPRUHX5I August 2014 – May 2024 TMS320F28374S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378S , TMS320F28379S
ADC offset error is determined and calibrated during factory testing. However, the user still has the option to perform offset calibration if the end application specifically requires this. This section describes how to perform offset calibration using internal VREFLO connection for single-ended operation, and external channels for differential operation.
Zero offset error is defined as the difference from 0 that occurs when converting a voltage at VREFLO (for single-ended operation), or the difference from MAX_CODE/2 when converting ADCINxP = ADCINxN (for differential mode). The zero offset error can be positive or negative. To correct this error, an adjustment of equal magnitude and opposite polarity is written into the ADCOFFTRIM register. The value contained in this register is applied before the results are available in the ADC result registers. This operation is fully contained within the ADC core, so the timing of the results is not affected, and the full dynamic range of the ADC is maintained for any trim value.
Using the GetAdcOffsetTrimOTP(Uint16) function, the ADCOFFTRIM register can be loaded with the factory calibrated offset error correction. The user can modify the ADCOFFTRIM register to compensate for additional offset error induced by the application environment if desired, but this is not typically necessary to achieve data manual specified performance.
Use the following procedure to re-calibrate the ADC offset in 12-bit single-ended mode:
Use the following procedure to recalibrate the ADC offset in 16-bit differential mode: