st10f273m STMicroelectronics, st10f273m Datasheet - Page 146

• Manufacturer Part Number: st10f273m
• Description: 16-bit Mcu With 512 Kbyte Flash Memory And 36 Kbyte Ram
• Manufacturer: STMicroelectronics

Electrical characteristics
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For the complete set of parameters characterizing the ST10F273M 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
Section 24.7: A/D converter characteristics on page
τ 1
10 τ 2
=
V A
(
⋅
R SW
⋅
=
R S R F R L R SW R AD
-------------------------------------------------------------------------- -
10 R ⋅ L
F
+
+
:
R AD
R L
R S
R F
⋅
(
F
+
C S
=
R C C F
and C
=
C F
+
R EQ
)
R EQ
V AM
------------ - R F R S
⋅
I INJ
+
-------------------- -
2πf 0 C F
R F
C S
+
=
C P1
=
1
4000 C S
=
=
+
S
–
-------------- -
f C C S
and taking some margin (4000 instead of 2048),
R L
2.8ns
----------- -
2πf 0
+
1
1
=
+
C P2
⋅
=
–
995Ω
=
=
V AM
------------ -
I INJ
=
)
15.9µs
10MΩ
=
16nF
T
=
=
F
S
290ns
=
≅
, C
2.35mV
2.9kΩ
L
= 1µs
:
1kΩ
4kΩ
F
and R
S
<
:
A
1
-- - LSB
2
T
L
= 5V):
S
are defined. Some
= 1µs
137.
ST10F273M
S
is