A 5V CMOS chip for interpolation of sine/cosine signals

This paper describes an analog/digital CMOS chip for interpolation of sine /cosine signals coming from optoelectronic sensors used in incremental primary elements. The presented chip contains the current to voltage converters for sine, cosine and reference channel, the nonlinear network interpolator and the digital circuitry for serial pulse output and absolute position output. Peak to peak differential input currents in the range of 6µA to 16µA are processed with a 500 kHz signal bandwidth and an interpolation factor IF of 5 to 50. The interpolation is done by a special 30 MHz tracking scheme which is insensitive to signal noise so that wrong count errors are impossible. The chip is fabricated in a 1.2-micron double-poly/double-metal process.