ST10F272M-4Q3 STMICROELECTRONICS [STMicroelectronics], ST10F272M-4Q3 Datasheet - Page 140

• Manufacturer Part Number: ST10F272M-4Q3
• Description: 16-bit MCU with 256 Kbyte Flash memory and 20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Electrical characteristics
140/176
1.
2.
3.
4.
5.
For the complete set of parameters characterizing the ST10F272M 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 elements 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 allows minimization of
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 condition to be verified is if the time constants of the transients are really and
significantly shorter than the sampling period duration T
V A
10 τ 2
⋅
⋅
R S R F R L R SW R AD
-------------------------------------------------------------------------- -
Section 24.7: A/D converter characteristics on page
τ 1
=
=
F
+
:
10 R ⋅ L
(
R SW
R L
R S
R F
F
+
=
R C C F
and C
=
⋅
C F
+
R EQ
(
R EQ
C S
V AM
------------ - R F R S
+
I INJ
-------------------- -
2πf 0 C F
R F
+
=
R AD
+
=
1
4000 C S
=
+
S
C P1
–
-------------- -
f C C S
and taking some margin (4000 instead of 2048),
R L
----------- -
2πf 0
)
1
⋅
1
=
+
C S
⋅
=
+
–
995Ω
=
=
C P2
V AM
------------ -
I INJ
=
=
15.9µs
10MΩ
16nF
2.8ns
=
=
)
F
=
≅
, C
=
2.35mV
2.9kΩ
L
:
1kΩ
4kΩ
290ns
F
and R
<< T
S
<
:
S
A
1
-- - LSB
2
< T
L
= 1µs
= 5V):
are defined. Some
S
= 1µs
131.
ST10F272M
S
is