iC-MSB is a signal conditioner with line drivers for sine/cosine sensors which are used to determine positions in linear and angular encoders, for example. Programmable instrumentation amplifiers with selectable gain levels permit differential or referenced input signals; at the same time the modes of operation differentiate between high and low input impedance. 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 integrated signal conditioning unit allows signal amplitudes and offset voltages to be calibrated accurately and also any phase error between the sine and cosine signals to be corrected. Separate zero signal conditioning settings can be made for the gain and offset; data is then output either as an analog or a differential square-wave signal (low/high level analogous to the sine/cosine amplitude). For the stabilization of the sine and cosine output signal levels a control signal is generated from the conditioned and calibrated input signals which can power the transmitting LED of optical systems via the integrated 50 mA driver stage (output ACO). If MR sensors are connected this driver stage also powers the measuring bridges. By tracking the sensor energy supply any signal variations and temperature and aging effects can be compensated for and the set signal amplitude maintained with absolute accuracy. At the same time the control circuitr y monitors both whether the sensor is functioning correctly and whether it is properly connected; signal loss due to wire breakage, short circuiting, dirt or aging, for example, is recognized when control thresholds are reached and indicated at alarm output ERR.
iC-MSB is protected against a reversed power supply voltage; the integrated voltage switch for loads of up to 20 mA extends this protection to cover the overall system. The analog output drivers are directly cable compatible and tolerant to false wiring; if supply voltage is connected up to these pins, the device is not destroyed. The device configuration and calibration parameters are CRC protected and stored in an external EEP ROM; they are loaded automatically via the I2C interface once the supply voltage has been connected up. A safety-technical analysis of iC-MSB on device level with the inclusion of layout and internal/external circuitry has been carried out together with the BGIA, St. Augustin. The result proved iC-MSB’s capability for safety oriented applications with Siemens Sinumerik Controls.