Siemens ASIC SIM 1-2, Function Manual

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Functional Description of the SIM 1-2
SIM 1-2
C79000-G8976-C215-01
21
Tolerance Calculation
The tolerance of I
BUS
, V
E
and V
REG
is made up the tolerance of the chip and the
tolerance of the reference resistors used R
RIREF
, R
RVCCVE
, R
RVREG
, R
RISOLL
, R
SENSEM
and R
SENSEP
. The precise relationships can be seen in the following formulas.
d
IBUS
= |d
SIM 1-2
| + |d
RRISOLL
| + |d
RRIREF
| + ( β
(T1)
/ ( β
(T1)
+ 1)) * |d
RSENSEP
| + (1 / ( β
(T1) +
1)) * |d
RSENSEM
|
d
VE
= |d
SIM 1-2
| + |d
RRVCCVE
| + |d
RRIREF
|
d
VREG
= |d
SIM 1-2
| + |d
RRVREG
| + |d
RRIREF
|
The tolerance of the parameters of I
BUS
, V
E
and V
REG
over the entire temperature
range (assuming a circuit with almost ideal reference resistors) is ±3 %; it
therefore follows that: d
SIM 1-2
= ±3 %.
2.3.8 Interface and Application Voltage VREG
With VREG, there is an operating voltage regulated by R
RVREG
in the range from 2
V to 5 V for local loads. This is also the power supply for the outputs and inputs of
the digital interface (TXE, TXS, RXA, RXS, RESETXN, PDWNXN).
2.3.9 Internal Power Supply: VCCD/VCCA, VM
The two pins VCCD and VCCA must be connected directly with each other and
backed up to GND over the capacitor C
VCC
.
No power for local loads may be taken from the internal power supply VCC.
The VM pin must be backed up to GND by capacitor C
VM
.
2.3.10 Oscillator: XT0, XT1
Pins XT0 and XT1 are provided for the connection of a 2 MHz quartz/ceramic
oscillator. Further external components (capacitances) are required depending on
the quartz/ceramic oscillator used. With external clock supply, XT0 is connected to
GND and XT1 is used as an input.
XT0 and XT1 may each be loaded with a capacitance of ≤ 47 pF.