iC-MQ
PROGRAMMABLE 9-BIT
Sin/Cos INTERPOLATION IC WITH RS422 DRIVER
Rev D4, Page 2/39
DESCRIPTION
Interpolator iC-MQ 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 reso-
lution per sine period can be set using SELRES; up
to 400 angle steps are possible (see page 26).
The angle position is output incrementally by differ-
ential 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.
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 permits
glitch-free output signals and prevents counting er-
rors 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; via input X2 the external ref-
erence can be used as reference voltage for the off-
set 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 di-
rectly 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 accu-
rately and also any phase error between the sine and
cosine signals to be corrected. The channel for the
zero signal can be configured separately.
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
measuring bridges. By tracking the sensor energy
supply any temperature and aging effects are com-
pensated for, the input signals stabilized and the ex-
act calibration of the input signals is maintained. This
enables a constant accuracy of the interpolation cir-
cuit across the entire operating temperature range.
When control limits are reached, these can be indi-
cated at the maskable error pin ERR. Faults such as
overdrive, wire breakage, short circuiting, dirt or ag-
ing, for example, are logged.
iC-MQ includes extensive self-test and system diag-
nosis functions which check whether the sensor is
working properly or not. For all error events the user
can select whether the fault be displayed at error pin
ERR or the outputs shutdown. At the same time er-
rors can be stored in the EEPROM to enable failures
to be diagnosed at a later stage. For encoder ap-
plications the line count of the code disc, the sensor
signal regarding signal level and frequency and the
operating temperature can be monitored, for exam-
ple, the latter using an adjustable on-chip sensor.
Display error pin ERR is bidirectional; a system fault
recognized externally can be recorded and also reg-
istered in the error memory.
iC-MQ is protected against reverse polarity and of-
fers its monitored supply voltage to the external cir-
cuit, thus extending the protection to the system (for
load currents 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 exter-
nal EEPROM and verified by a CRC. A microcon-
troller can also configure iC-MQ; the implemented in-
terface is multimaster-competent and enables direct
RAM access.
ICHAUS [ IC-HAUS GMBH ]
