iC-PT 3310 is an optical sensor IC with integrated photosensors whose signals are converted into voltages by low-noise transimpedance ampliﬁers. Precise voltage comparators with hysteresis are used to generate the digital signals, supplied to the output pins via differential +/- 4 mA push-pull drivers.
The built-in LED power control with its 40 mA driver stage permits a direct connection of the encoder LED. Regardless of aging or changes in temperature the received optical power is kept constant. An external resistor presets the photocurrent operating point and thus the desired illumination level.
Selection input SEL chooses for three different operating modes: regular A/B operation, A/B operation with 2-fold interpolation, or analog operation. With analog operation the ampliﬁed signal voltages are available at the outputs for inspection and monitoring encoder assembly.
Typical applications of iC-PT devices are incremental encoders for motor feedback and commutation. To this end, device version iC-PT 3310 provides differential A/B tracks and a differential index track, each consisting of multiple photo sensors. The layout of the signal ampliﬁers is such that there is an excellent paired channel matching, eliminating the needs for signal calibration in most cases.
Additionally, three more tracks are provided to generate motor commutation information for the U, V and W outputs, for instance with 120 degree phase shift to operate 3-phase brushless motors (period count and phase shift can be varied by the code disc applied).