IC-MQF_15 Datasheet, PDF (20/38 Pages) IC-Haus GmbH – Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQF PROGRAMMABLE 12-BIT ^preliminary
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
INPUT CONFIGURATION AND SIGNAL PATH MULTIPLEXER
Rev C1, Page 20/38
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 R12 and R0.
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.
Figure 4: 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().
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.
R12
R0
Code
–000
–010
–100
–110
1—1
0—1
Notes
Addr 0x05, bit 3:0
Addr 0x04, 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
When using X2 as reference input for single-ended
signals use R12 = R0.
*) VREFin is the voltage divider’s footpoint. Input
currents may be positive or negative (Vin > VREFin,
or Vin < VREFin)
Table 16: I/V Mode and Input Resistance
BIAS12
BIAS0
Code
0
1
Notes
Addr 0x05, bit 6
Addr 0x04, 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 currrent-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)
When using X2 as reference input for single-ended
signals use BIAS12 = BIAS0.
Table 17: Reference Voltage