|Sensor chips for optical position encoders with photodiodes designed especially for blue light|
The new encoder chips of the iC-PT H-Series combine optimized scanning and signal interpolation in the smallest available space: a flat 5 x 5 mm≤ optoQFN package with a plane window. Due to the optimized Phased-Array structure of the opto-chips, a minimal scanning area of only 1.9 mm x 3.1 mm is sufficient to generate 10,000 pulses per revolution using a code disc of only 26 mm diameter, for example. The blue light increases the contrast with lower noise and the improved efficiency reduces the current consumption within the optical system.
The devices generate low-jitter encoder quadrature signals with index via 4 mA push-pull drivers in single, double and four-fold resolution for precise motor regulation. Besides, conventional Hall sensors used for motor commutation have been replaced by the integration of three additional scanning tracks. Here, the code disc determines the required commutation signal and can be easily adapted to suit the required motor pole count.
The index gating as well as the interpolation is easily selectable by pin. Output frequencies of up to 1.6 MHz are permitted, enabling motor speed control at up to 10,000 rpm with 10,000 pulses per revolution. Analog test signals can be activated for ease of alignment and test of the complete encoder assembly.
The small scanning area and high sensitivity both help to reduce the power requirements of the encoder LED Ė and operating current of a few milliamps is sufficient. This improves the LEDís lifetime, especially at high operating temperatures. The iC-PT H devices control the LED and compensate for aging and temperature effects.
Evaluation boardsEvaluation boards for the scanners together with plastic code discs and snap-on blue LEDs to allow judging the signal quality benefits in a direct comparison with IR illumination are available. The higher forward voltage of blue LEDs and the integrity of the materials used within the encoder have to be considered at system design.
Product iC-PT H-Series