Introduction
The Si1102 and Si1120 are low-cost, high-performance, active-optical reflectance-based proximity sensors. Both drive an LED to illuminate a target, then measure the reflectance from the target to determine its proximity.
Both the Si1102 and Si1120 use short-duration strobe pulses to measure reflectance. This keeps the average power consumption in the microwatt range. Both devices cancel background dc ambient before making a reflectance measurement. The reflectance measurement is the difference between the dc ambient and dc ambient plus reflection from the target illuminated by the LED.