IC-MQ_15 Datasheet, PDF (19/43 Pages) IC-Haus GmbH – Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQ PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
INPUT CONFIGURATION
Rev F3, Page 19/43
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, selected
using RIN12 and RIN0.
INMODE
Code
0
1
Note
Addr 0x03, bit 2
Function
Differential input signals
Single-ended input signals *
* Input X2 is reference for all inputs.
Table 16: Input Signal Mode
Figure 3: Signal conditioning input circuit.
Current Signals
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 re-
sistor and resistor Rui() which is linked to the adjustable
bias voltage source VREFin(). BIASEX must be set to
’00’.
The table besides shows the possible selections, with
Rin() giving the typical resulting input resistance (see
Electrical Characteristics for tolerances). The input re-
sistor should be set in such a way that intermediate
potentials VDC1 and VDC2 lie between 125 mV and
250 mV (verifiable in mode Calibration 2).
NB. The input circuit is not suitable for back-to-back
photodiodes.
Voltage Signals
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 calibration is to be propor-
tional to an external DC voltage source the reference
source can be selected using BIASEX; for all other
sensors BIASEX should be set to ’00’.
RIN12
RIN0
Code
–000
–010
–100
–110
1—1
0—1
Notes
Addr 0x0E, bit 3:0
Addr 0x13, bit 3:0
Nominal Rin() Internal Rui() I/V Mode
1.7 kΩ
1.6 kΩ
current input
2.5 kΩ
2.3 kΩ
current input
3.5 kΩ
3.2 kΩ
current input
4.9 kΩ
4.6 kΩ
current input
20 kΩ
5 kΩ
voltage input 4:1*
high
impedance
1 MΩ
voltage input 1:1
For single-ended signals identical settings of RIN0
and RIN12 are required.
*) VREFin is the voltage divider’s footpoint. Input
currents may be positive or negative (Vin > VREFin,
or Vin < VREFin)
Table 17: I/V Mode and Input Resistance
BIAS12
BIAS0
Code
0
1
Addr 0x0E, bit 6
Addr 0x13, bit 6
Function
VREFin = 2.5 V
for low-side current sinks (e.g. photodiodes with
common anode at GNDS)
VREFin = 1.5 V
for high-side current-sources (e.g. photodiodes with
common cathode at VDDS)
for voltage sources versus ground
(e.g. iC-SM2, Wheatstone sensor bridges)
for voltage sources with low-side reference
(e.g. iC-LSHB, when using BIASEX = 11)
Table 18: Reference Voltage
BIASEX
Code
00*
10
11
Notes
Addr 0x0D, bit 7:6
VREFin
Pin function of X2
internal
Input Index- (negative zero signal)
internal
Output of VREFin12*
external
Input for external reference**:
V(X2) replaces VREFin
*) Do not load, buffering recommended
**) See Elec. Char. Nos. 122 and 123
Table 19: Input Reference Selection