ST10F272B_12 STMICROELECTRONICS [STMicroelectronics], ST10F272B_12 Datasheet - Page 149

• Manufacturer Part Number: ST10F272B_12
• Description: 16-bit MCU with 256 Kbyte Flash memory and 12/20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST10F272B/ST10F272E
Example of external network sizing
The following hypothesis are formulated in order to proceed in designing the external
network on A/D Converter input pins:
●
●
●
●
●
●
●
●
●
●
●
1.
Equation 10
2.
Equation 11
3.
Equation 12
4.
Equation 13
from which is now simple to define the value of R
Analog Signal Source Bandwidth (f
conversion Rate (f
Sampling Time (T
Pin Input Capacitance (C
Pin Input Routing Capacitance (C
Sampling Capacitance (C
Maximum Input Current Injection (I
Maximum Analog Source Voltage (V
Analog Source Impedance (R
Channel Switch Resistance (R
Sampling Switch Resistance (R
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:
S
C
):1μs
):25kHz
F
:
P1
Doc ID 11917 Rev 3
S
):4pF
):5pF
R S
R F
F
S
R C C F
SW
and C
=
C F
+
):100Ω
AD
-------------------- -
2πf 0 C F
R F
):500Ω
P2
=
):200Ω
INJ
0
1
):1pF
):10kHz
4000 C S
AM)
=
+
S
):3mA
and taking some margin (4000 instead of 2048),
R L
----------- -
2πf 0
:12V
1
=
⋅
=
995Ω
=
V AM
------------ -
I INJ
=
L
15.9μs
:
16nF
=
≅
1kΩ
4kΩ
Electrical characteristics
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