AN3137 datasheet(7/42 Pages) STMICROELECTRONICS

Part #	AN3137

Description	Analog-to-digital converter on STM8L and STM8AL devices

PDF	42 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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AN3137

STM8L/STM8AL ADC internal hardware

Doc ID 16983 Rev 3

7/42

STM8L/STM8AL ADC internal hardware

STM8L/STM8AL microcontrollers can include an ADC. This ADC peripheral is used to

measure analog signals from external signal sources.

1.1

ADC principle

The ADC in STM8L/STM8AL microcontrollers is a 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.

The following figures (Figure 1 to Figure 6) explain the principle of ADC operation. They are

based on a 10-bit ADC example (whereas STM8L/STM8AL devices contain a 12-bit ADC).

The example given below shows only the first steps of approximation but the process

continues till the LSB is reached.

Figure 1.

Basic schematic of switched-capacitor 10-bit ADC

Basic ADC schematic with digital output.

AN3137 Datasheet(PDF) 7 Page - STMicroelectronics