Part # Application Note General Purpose datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: ST6 - Microcontroller (MCU) and TRIACs on the mains (110 220V)

Part Details:

APPLICATION NOTE Expanding A/D Resolution at the ST6 A/D Converter P. MALUSARDI INTRODUCTION Occasionally the analog signal provided by external sensors require an Analog to Digitalconversion with a resolution of greater than 8 bits. In order to extract the full information forsubsequent data processing within the microcontroller a higher resolution Analog to Digital isthus required.The solution described in this note enables this higher resolution with the on-chip 8-bit A/Dconverter of the ST62, using only an additional Operational Amplifier (OpAmp) and a fewresistors. 1 OVERVIEW The technique implemented is that of the Algebraic Adder, a full discussion of the principle ofoperation is included in this note. A practical example of the external components used is shown in the following figure: Figure 1. Example circuit PC4 PC5 OUTPUTS PC6 ST6215 PB0 (A/D Input) Vin The resistances are selected by the ST62 I/O pins depending on the analog input voltage.The selection programmed modifies the output voltage of the OpAmp in such a way that thefollowing A/D conversion is always made with the maximum input range of the converter.This selection is made by software, therefore the total conversion time is increased versus anormal 8-Bit conversion, however the precision is increased and the input voltage range canbe enlarged. AN420 / 02,94 EXPANDING A/D RESOLUTION AT THE ST6 A/D CONVERTER 2 PRINCIPLE OF OPERATION OF AN ALGEBRAIC ADDER Figure 2 represents the generic algebraic adder. Figure 2. Generic algebraic adder RNn VNn RN2 Rr VN2 RN1 Vn + VN1 RN0 Vo RP1 - VP1 Vp RP2 VP2 RP0 RPm VPm The circuit generates an output voltage equal to: m n V = × - × 0 Ki VP

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Application Note General Purpose.pdf Datasheet