iC-MR 13-BIT S&H SIN/COS
INTERPOLATOR WITH CONTROLLER INTERFACES
Rev A1, Page 2/44
DESCRIPTION
Device iC-MR is a universal sine-to-digital converter The control unit operating limits are also monitored
with signal conditioning and various interfaces for so that an alarm can be signaled through the I/O in-
configuration and data communication. Microcon- terface and/or at error output NERR, depending on
trollers can be connected up through a parallel I/O the configuration, with dirt or ageing of optical sys-
interface with an 8-bit bus width (12.5 MHz) or using tems.
a serial I/O interface (4-pin SPI, 20 MHz). The serial
I/O interface can function as a sensor interface either Sine-to-digital conversion is performed by a fast inter-
in BiSS C protocol (up to 10 MHz, bidirectional) or in polator with a sample-&-hold circuit which resolves a
SSI protocol (up to 4 MHz).
sine period with 13 bits either continuously or on re-
quest. In parallel and independent of the interpola-
In the analog signal path iC-MR has precision input tor a configurable 37-bit period counter logs the sine
amplifiers with an adjustable gain for differential or and cosine zero crossings. This period counter is
referenced voltage signals of 10 mV peak to 1 V peak programmable and can take its start value from the
or for current signals of approx. 10 µA to 300 µA (in- serial absolute data interface (ADI); the correspond-
put pins PSI, NSI, PCI, and NCI). A separate mea- ing interface master operates either in BiSS C or SSI
surement input (VREF) enables signals to be refer- protocol.
enced to the sensor’s reference voltage.
For position measurement applications iC-MR differ-
The downstream signal conditioning unit can com- entiates between multiturn and singleturn data using
pensate for typical sine/cosine sensor signal errors, a selectable intersection on the period counter. The
such as offset, amplitude, and phase errors. The position can be corrected accordingly using the mul-
conditioned signals are filtered and output through titurn and singleturn offset values.
analog line drivers with an amplitude of typically
250 mV (output pins PSO, NSO, PCO, and NCO). A An integrated 12-bit A/D converter digitizes linear
differential 1 Vpp signal to 100 Ω is available for line measurement voltages at pin ADC for the evaluation
transmission.
of KTY temperature sensors, for example. Measure-
ment of the calibratable converter is observed by set-
A control signal is gained from the conditioned sig- table threshold values so that a permissible operating
nals to stabilize the sine/cosine output signals. This temperature range with a lower and upper tempera-
can adjust the transmitting LED of optical encoder ture threshold can be monitored.
systems using the integrated 50 mA driver stage (out-
put ACO). With magnetic sensors this driver output After power-on iC-MR collects its CRC protected
supplies the MR measuring bridges or can be used configuration data from an external I2C-EEPROM or
to feedback the bridge supply voltage. By tracking waits for the configuration from one of the I/O inter-
the sensor supply, sensor temperature and ageing ef- faces. An undervoltage reset zeroes internal reg-
fects are compensated for, the input signals are sta- isters and is shown as a reset pulse at pin NRES,
bilized, and precise calibration of the input signals is which also serves as a reset input (low active).
maintained. This makes a constant interpolation ac-
curacy possible across the entire operating tempera- Errors can always be masked and allocated to an
ture range.
error byte (and displayed at error message output
NERR) or a warning byte. The internal status reg-
At the same time the sensor is monitored for proper isters are available to the I/O interfaces which have a
functioning. The amplitude and offset of the input sig- number of different commands (software reset, mem-
nals at pins PSI, NSI, PCI, and NCI are checked, en- ory verification, and error simulation).
abling wire-breakage or short circuits to be detected.
ICHAUS [ IC-HAUS GMBH ]
