ST STM8S Getting Started page 11

AN2752
Equation 1:
C C
=
VIN
where:
•
C
VIN
•
C
SAMP
•
C
EXT
parasitic routing capacitance, pad and pin capacitance and external capacitance. To
ensure proper and accurate sampling the following equation must be satisfied
Equation 2:
(
R R
+
SW
where:
•
R
SW
•
R
EXT
•
C
SAMP
•
T = 0.5 µs (for 2 MHz input CLK)
S
Equation 2
ADC.
Refer to the STM8S or STM8AF datasheets and/or to reference manual RM0016 (available
on www.st.com) for more details.
C
+
SAMP EXT
is the total equivalent capacitor on the path of V
is the equivalent sampling capacitance
is the total external capacitance on the path of V
) × ( )
C C
+
EXT SAMP EXT
= 30 kΩ
is the total external resistance on the path of V
= 3 pF
is specific for R
EXT
3
⎛ ⎞
< ×
T
----- -
⎝ ⎠
S
10
and C when designing an analog input interface for the
EXT
AN2752 Rev 6
Analog-to-digital converter (ADC)
IN
to the macro pin. This includes
IN
IN
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