Siemens ASIC SIM 1-2, Руководство по эксплуатации функций

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Functional Description of the SIM 1-2
SIM 1-2
C79000-G8976-C215-01
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Input Impedance
To achieve the impedance of 3 k Ω required by IEC 61158-2 at the bus attachment
terminals in conjunction with the transistor PZT3906, the EMC capacitances
parallel to the bus connector must be limited as follows:
2 mA < I
BUS
≤ 15 mA, C
EMC
≤ 500 pF
Starting at an I
BUS
current of 15 mA, the capacitance of C
EMC
must be reduced
continuously. This results in a curve with the following vertices:
I
BUS
C
EMC
20 mA C
EMC
≤ 340 pF
30 mA C
EMC
≤ 190 pF
40 mA C
EMC
= 0 pF
As of a current of ≥ 40 mA, C
EMC
remains = 0 pF.
At I
BUS
currents > 40 mA, the required impedance (at 39 kHz) for bus voltages U
BUS
< 12 V is not achieved.
System Stability
We recommend the transistor PZT3906.
If you set the I
BUS
current to ≥ 30 mA, you should use an additional L_SENSE
inductor of 1 µH. This avoids self-excitation and increases system stability.
The L_SENSE inductor is connected in series with R_SENSEP and is not included
in the layout proposal in this manual.
As the inductor, we recommend the B82422H from the EPCOS series. If
necessary, correct the value of R_SENSEP to achieve the required 10
Ω with the
desired accuracy.
SENSEM
SENSEP
R_SENSEM R_SENSEP L_SENSE
2
3