ST10F271E STMICROELECTRONICS [STMicroelectronics], ST10F271E Datasheet - Page 145

• Manufacturer Part Number: ST10F271E
• Description: 16-bit MCU with 128 Kbyte Flash memory and 8/12 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST10F271B/ST10F271E
1.
2.
3.
4.
5.
For complete set of parameters characterizing the ST10F271 A/D Converter equivalent
circuit, refer to
Supposing to design the filter with the pole exactly at the maximum frequency of the
signal, the time constant of the filter is:
Using the relation between C
it is possible to define C
As a consequence of step 1 and 2, RC can be chosen:
Considering the current injection limitation and supposing that the source can go up to
12V, the total series resistance can be defined as:
from which is now simple to define the value of R
Now the three element of the external circuit R
conditions discussed in the previous paragraphs have been used to size the
component, the other must now be verified. The relation which allow to minimize the
accuracy error introduced by the switched capacitance equivalent resistance is in this
case:
So the error due to the voltage partitioning between the real resistive path and C
less then half a count (considering the worst case when V
The other conditions to be verified is the time constants of the transients are really and
significantly shorter than the sampling period duration T
Section 24.7: A/D converter characteristics on page 136
10 τ 2
V A
⋅
⋅
τ 1
R S R F R L R SW R AD
-------------------------------------------------------------------------- -
=
=
F
+
10 R
:
(
R SW
R L
⋅ L
R F
R S R F R L
F
+
=
R C C F
C F
and C
=
R EQ
⋅
+
R EQ
+
V AM
------------ - R F R S
(
I INJ
-------------------- -
2πf 0 C F
=
C S
R AD
+
4000 C S
=
1
=
+
S
+
–
-------------- -
f C C S
)
and taking some margin (4000 instead of 2048),
C P1
----------- -
2πf 0
⋅
1
1
⋅
=
=
+
C S
–
995Ω
=
V AM
------------ -
I INJ
=
+
=
=
C P2
15.9µs
10MΩ
16nF
F
2.8ns
=
=
, C
=
≅
L
2.9kΩ
)
2.35mV
4kΩ
:
=
F
1kΩ
and R
290ns
<< T
S
<
:
S
A
L
1
-- - LSB
2
< T
= 1µs
= 5V):
are defined. Some
Electrical characteristics
S
= 1µs
.
145/180
S
is