ST STM8S Application Note

Analog-to-digital converter (ADC) AN2752
10/42 Doc ID 14651 Rev 3
3 Analog-to-digital converter (ADC)
3.1 Analog power
The ADC unit has an independent, analog supply reference voltage, isolated on input pin
V
DDA
, which allows the ADC to accept a very clean voltage source. This analog voltage
supply range is the same as the digital voltage supply range on pin V
DD
. An isolated analog
supply ground connection on pin V
SSA
provides further ADC supply isolation. Together, the
analog supply voltage and analog supply ground connection, offer a separate external
analog reference voltage input for the ADC unit on the V
REF+
pin. This gives better accuracy
on low voltage input as follows:
● V
REF+
(input, analog reference positive): The higher/positive reference voltage for the
ADC should be between [250 mV, V
DDA
]. For more details about V
REF+
values please
refer to the Root part number 2 datasheet. This input is bonded to V
DDA
in devices that
have no external V
REF+
pin (packages with 48 pins or less).
● V
REF-
(input, analog reference negative): The lower/negative reference voltage for the
ADC should be higher than V
SSA
. For more details about V
REF-
values please refer to
the Root part number 2 datasheet. This input is bonded to V
SSA
in devices that have no
external V
REF-
pin (packages with 48 pins or less).
3.2 Analog input
Root part number 2 devices have 16 analog input channels, which are converted by the
ADC one at a time, and each multiplexed with an I/O.
The analog input interface of the ADC is shown in Figure 4.
Figure 4. Analog input interface
V
IN_EXT
R
EXT
C
EXT
C
SAMP
SW
SAMP
V
IN
Outside ADC Inside ADC

ST STM8S Specifications

General

Brand	ST
Model	STM8S
Category	Microcontrollers
Language	English