Drive-control interface IC for sine/cosine encoders has integrated safety functions

September 19, 2014 // By Graham Prophet
Designed to provide fast and safe position acquisition with sine/cosine encoders and linear systems, the iC-MR provides 13-bit sine-to-digital conversion with condition monitoring for linear and rotational encoders

A complete position sensor and encoder interface in a “system-on-chip” solution, intrinsically safe differential sine/cosine transmission of position information runs at signal frequencies of up to 500 kHz.

The circuitry contains serial and parallel MCU interfaces; a complete analogue front end for signal conditioning; a 13-bit sample and hold SAR tangent converter with a latency of 2 µsec; diagnostic functions for monitoring the sine/cosine signals in real time; and a a 1V output driver for a differential sin/cos output at 100Ω.

A combined singleturn/multiturn period counter with a length of up to 50 bit supports real time processing in the drive controller even at high sine/cosine signal input frequencies. Additional safety functions in the iC-MR monitor the sine/cosine input signal level, detect short-circuit and wire breakage, monitor the control range if supplying an external encoder LED or an MR sensor measuring bridge, monitor a motor temperature sensor, and finally secure the data transmission through a life counter as well as by an extended CRC generation. Measurement of the motor temperature, for example through a KTY sensing element, occurs through an adjustable 12-bit A/D converter featuring range monitoring and in that way, supports an active condition monitoring function through the drive controller.

For sensor-based applications, inside a magnetic or an optical encoder, differential or referenced sensor signals of a few millivolt upwards – generated by MR sensor bridges or photo sensors – for example, can be amplified and conditioned in offset, amplitude and phase. A regulated current output maintains the adjusted measuring accuracy during operation by readjusting the supply of the LED light source or the magnetic sensor bridge. Compensation of temperature and ageing effects occurs automatically, if necessary.