IC-MQF_15 Datasheet, PDF (2/38 Pages) IC-Haus GmbH – Sin/Cos INTERPOLATION IC WITH RS422 DRIVER

iC-MQF PROGRAMMABLE 12-BIT ^preliminary
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev C1, Page 2/38
DESCRIPTION
Interpolator iC-MQF is a non-linear A/D converter
which digitizes sine/cosine sensor signals using a
count-safe tracking conversion principle with se-
lectable resolution and hysteresis. The angle res-
olution per sine period can be set using SELRES; up
to 4000 angle steps are possible (see page 27).
The angle position is output incrementally by differen-
tial RS422 drivers as an encoder quadrature signal
with a zero pulse or, if selected, as a counter signal
for devices compatible with 74HC191 or 74HC193.
A control signal is generated from the conditioned
signals which can track the transmitting LED of op-
tical encoders via the integrated 50 mA driver stage
(output ACO). If MR sensors are connected this driver
stage can also track the power supply of the measur-
ing bridges. By tracking the sensor energy supply any
temperature and aging effects are compensated for,
the input signals stabilized and the exact calibration
of the input signals is maintained. This enables a
constant accuracy of the interpolation circuit across
the entire operating temperature range.
The zero pulse is generated electronically when an
enable has been set by the X1/X2 inputs. This pulse
can be configured extensively: both in its relative po-
sition to the input signal with regard to the logic gating
with A and/or B and in its width from 90° to 360° (1/4
to 1 T).
A preselectable minimum transition distance ensures
glitch-free output signals and prevents counting errors
which in turn boosts the noise immunity of the position
encoder.
Programmable instrumentation amplifiers with se-
lectable gain levels allow differential or single-ended,
referenced input signals; a external reference can be
used via input X2 as reference voltage for the offset
correction.
The modes of operation differentiate between high
impedance (V modes) and low impedance (I modes).
This adaptation of the iC to voltage or current signals
enables MR sensor bridges or photosensors to be
directly connected up to the device. The optical scan-
ning of low resolution code discs is also supported by
the reference function of input X2; these discs do not
evaluate tracks differentially but in comparison with a
reference photodiode.
The integrated signal conditioning unit allows signal
amplitudes and offset voltages to be calibrated ac-
curately and any phase error between the sine and
cosine signals to be corrected. The channel for the
zero signal can be configured separately.
If control limits are reached, these can be indicated
at the maskable error pin ERR. Faults such as over-
drive, wire breakage, short circuiting, dirt or aging, for
example, can be logged.
iC-MQF includes extensive self-test and system di-
agnosis functions which check whether the sensor is
working properly or not. For all error events the user
can select whether the fault is indicated at the pin ERR
or whether the outputs should shutdown. At the same
time errors can be stored in the EEPROM to enable
failures to be diagnosed at a later stage. For encoder
applications the line count of the code disc, the sensor
signal regarding signal level and frequency and the
operating temperature can be monitored, for example,
the latter using an adjustable on-chip sensor.
Display error pin ERR is bidirectional; a system fault
recognized externally can be recorded and also regis-
tered in the error memory.
iC-MQF is protected against reverse polarity and of-
fers its monitored supply voltage to the external circuit,
thus extending the protection to the system (for load
currents up to 20 mA). Reverse polarity protection
also covers the short-circuit-proof line drivers so that
an unintentional faulty wiring during initial operation is
tolerated.
On being activated the device configuration is loaded
via the serial configuration interface from an external
EEPROM and verified with a CRC. A microcontroller
can also configure iC-MQF; the implemented inter-
face is multimaster-competent and allows direct RAM
access.