AN2719

STM8 ADC internal hardware

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1.2

ADC clock

The ADC is driven by a clock derived from the MCU master clock through a programmable

divider. This allows you to select the ADC clock speed according to your application

requirements. The conversion and sampling speed depends on ADC clock. Each

conversion step (described in Figure 4 to Figure 6 ) is performed in one ADC clock cycle - so

10-bit conversion takes 10 cycles. The sampling period is 3 clocks and the synchronisation

period takes 1 clock. The total conversion time is actually 14 cycles.

1.3

Reference voltage

The reference voltage is either internally connected to analog power supply pins or

connected to external pins where you can connect a reference voltage source. This

reference voltage connection option depends on the given STM8 package and STM8 device

type. The reference voltage has big influence to ADC precision, therefore care must be

taken with it in the application design (stability, noise, ...).

1.4

Multiplexer

The ADC has an input multiplexer which is used to select one of the STM8 input pins as the

analog input to the ADC.