
6-channel incremental optical encoder IC for electronic motor commutation
The optimized phased array structure of the photochips means that a minimal scanning area of just 1.9×3.1mm is enough to generate 2,500 pulses from a code disc measuring only 26 mm across, for example. While the iC-PT sensors are designed for standard diameters of 26 mm (iC-PT2613) and 33 mm (iC-PT33xx), the iC-LTA is a functionally compatible yet unstructured photo array for specific customized design. The Hall sensors used for motor commutation to date have been replaced by three separate on-chip scanning tracks. Here, the code disc stipulates the required signal and can be easily designed to suit the required motor pole count. The photocurrent signals are conditioned by low-noise CMOS amplifiers and can either be compared or interpolated twice, output through 4 mA push/pull drivers as indexed encoder quadrature signals. Output frequencies of up to 800 kHz are permitted, enabling motors with speeds of up to 20,000 rpm to be controlled (at 2,500 pulses). Analog test signals can be activated for assembly and alignment. The iC-LTA and iC-PT control the LED themselves and also compensate for fluctuations in the operating temperature range of -40 to +120°C.
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