description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196.2.1Program flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206.2.2Hardware and software requirements . . . . . . . . . . . . . . . . . . . . . . . . . . 207Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21STM8 ADC internal hardwareAN27194/22 1 STM8 ADC internal hardware STM8 family microcontrollers include an Analog to Digital Converter of the switched-capacitor type. This ADC type uses the SAR (Successive Approximation Register) principle, by which the conversion is performed in several steps. The number of conversion steps is equal to the number of bits in the ADC converter.1.1 SAR principleFigure1 to Figure6 show the first conversion steps.Figure 1.Basic schematic of switched-capacitor ADCFigure 2.Sample phaseS1 CLK DQ CLR PR A2ADCclkataADCclk456783288S1AS2SaVrefVin 2C Vcomp = 0Equivalent ci specifications: temperature drift, voltage noise, and load regulation (input resistance of reference input on STM8 ADC converter is >60 k ).2.5.3 Temperature influenceTemperature has a big effect on ADC precision. Mainly two specifications are important: offset drift and gain drift. Those errors can be compensated in microcontroller firmware. One method is to fully characterize the offset and gain drift and provide a lookup table in memory to correct measurement due to temperature change. The ADC in each MCU device must then be compensated individually - therefore this calibration takes additional cost and time. The second method is to recalibrate the ADC when temperature change reaches given values. The effect of temperature on ADC accuracy is usually not specified seperately for microcontrollers because it is lower than other effects. It is included in the values for the other error types.2.5.4 AC performanceUsually ADC performance is good only if input signals are from DC level up t datasheet. The datasheets also include sect