iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev D4, Page 19/39
INPUT CONFIGURATION
All input stages are configured as instrumentation am-
plifiers and thus directly suitable for differential input
signals. Referenced input signals can be processed;
input X2 can be configured as a reference input. Both
current and voltage signals can be processed, se-
lected using RIN12 and RIN0.
INMODE
Adr 0x03, bit 2
Code
0
Function
Differential input signals
Single-ended input signals *
* Input X2 is reference for all inputs.
1
Note
Figure 2: Signal Conditioning
Table 16: Input Signal Mode
RIN12
RIN0
Code
–000
–010
–100
–110
1—1
0—1
Adr 0x0E, bit 3:0
Current Signals
Adr 0x13, bit 3:0
In I Mode an input resistor Rin() becomes active at
each input pin, converting the current signal into a
voltage signal. Input resistance Rin() consists of a
pad wiring resistor and resistor Rui() which is linked
to the adjustable bias voltage source VREFin(). BIA-
SEX must be set to ’00’. The table besides shows the
possible selections, with Rin() giving the typical result-
ing input resistance (see Electrical Characteristics for
tolerances). The input resistor should be set in such
a way that intermediate potentials VDC1 and VDC2 lie
between 125 mV and 250 mV (verifiable in mode Cali-
bration 2).
Nominal Rin() Internal Rui()
I/V Mode
1.7 kΩ
2.5 kΩ
3.5 kΩ
4.9 kΩ
20 kΩ
1.6 kΩ
2.3 kΩ
3.2 kΩ
4.6 kΩ
5 kΩ
current input
current input
current input
current input
voltage input
voltage input
high
impedance
1 MΩ
Table 17: I/V Mode and Input Resistance
BIAS12
BIAS0
Code
0
Adr 0x0E, bit 6
Adr 0x13, bit 6
VREFin()
2.5 V
Voltage Signals
Type of sensor
In V mode an optional voltage divider can be selected
which reduces unacceptably large input amplitudes to
ca. 25 %. The circuitry is equivalent to the resistor
chain in I mode; the pad wiring resistor is considerably
larger here, however. For sensors whose offset cali-
bration is to be proportional to an external DC voltage
source the reference source can be selected using BI-
ASEX; for all other sensors BIASEX should be set to
’00’.
Lowside sink current (I Mode)
Highside current source (I Mode)
1
1.5 V
Note
Not valid with BIASEX=11.
Table 18: Reference Voltage
BIASEX
Code
00*
Adr 0x0D, bit 7:6
VREFin()
Signal at X2
1.5 / 2.5 V
(internal)
Neg. Zero Signal (Index -), input
10
11
1.5 / 2.5 V
(internal)
Ref. Voltage VREFin12, output
Voltage at X2 supplies VREFin
external
Table 19: Input Reference Selection
ICHAUS [ IC-HAUS GMBH ]
