st10f272z2 STMicroelectronics, st10f272z2 Datasheet - Page 154

• Manufacturer Part Number: st10f272z2
• Description: 16-bit Mcu With 256 Kbyte Flash Memory And 20 Kbyte Ram
• Manufacturer: STMicroelectronics

Electrical characteristics
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For complete set of parameters characterizing the ST10F272Z2 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 25.7: A/D converter characteristics on page
V A
10 τ 2
⋅
⋅
R S R F R L R SW R AD
-------------------------------------------------------------------------- -
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
F
4kΩ
290ns
and R
<< T
S
<
:
S
A
L
1
-- - LSB
2
< T
= 1µs
= 5 V):
are defined. Some
S
146.
= 1µs
ST10F272Z2
S
is