
DocID13284 Rev 2
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UM0404
Analog / digital converter
accuracy error introduced by the switched capacitance equivalent resistance is in this
case:
7.
So the error due to the voltage partitioning between the real resistive path and C
S
is
less then half a count (considering the worst case when V
A
= 5V):
8.
The other conditions to be verified is the time constants of the transients are really and
significantly shorter than the sampling period duration T
S
:
For complete set of parameters characterizing the ST10F276 A/D converter equivalent
circuit, refer to the datasheet.
R
EQ
1
f
C
C
S
---------------
10M
Ω
=
=
V
A
R
S
R
F
R
L
R
SW
R
AD
+
+
+
+
R
EQ
-------------------------------------------------------------
2.35mV
=
⋅
1
2
--- LSB
<
τ
1
R
SW
R
AD
+
(
)
=
C
S
2.8ns
=
⋅
<<
T
S
= 1
μ
s
10
τ
2
⋅
10 R
⋅
L
=
C
S
C
P1
C
P2
+
+
(
)
290ns
=
⋅
<
T
S
= 1
μ
s