iC-LSHB is an optical sensor IC with 6 integrated photodiodes whose signal currents are converted into output voltages by low-noise transimpedance ampliﬁers.
The IC is well suited for the operation of interpolation circuits for linear or rotary incremental encoders with an index signal. iC-LSHB thus has a shamrock-style sensor layout of four photodiodes, each with an active area of 800 µm x 330 µm. Both a positive and negative sine signal and a positive and negative cosine signal are generated from a single shared code track. The signal ampliﬁer layout ensures excellent paired channel matching, reducing signal differences to an absolute minimum.
Two separate photodiodes, with active areas of 1720 µm x 150 µm apiece, are employed for the differential scanning of the index track and to generate the zero signal.
The spectral sensitivity ranges from visible to near infrared light, with the maximum sensitivity close to a wavelength of 680 nm.
Due to a high transimpedance gain of typically 4 MΩ signal voltages of several hundred millivolts are obtained at low illumination levels. An output signal amplitude of 1 V is typical in low light conditions, for instance when iC-LSHB is illuminated at only by a 740 nm LED.0.2 mW/cm2.
A threefold intensity is sufﬁcient when using iC-LSHB for encoder applications with typical disc and mask codes. Therefore, a relatively low LED current is enough to operate the sensor, proving beneﬁcial to the life expectancy of the LED at high operating temperatures.
iC-LSHB is suitable for on-chip or LED-end mounting of the grating (reticle), so that the period count, signa waveform, phase shift and index marker code can be selected with ﬂexibility.