During device operation, the PRX, STX and TXO pins control the operation of the proximity detection system. The pulse width modulated PRX signal is output by the Si1120 and is a measure of the reflected IR energy. The TXO signal is a constant current sink for the IR LED which generates the energy that will be reflected off of the object in proximity. The STX signal is an input to the Si1120 and is used to start the measurement. As will be seen on a later slide, the STX signal can also be used to abort the measurement as well. Shown in the figure is a sample schematic using a single IR LED driven directly from the Si1120. There are no external gates required to drive the LED as the Si1120 can sink the constant current required. The STX and PRX signal can be connected directly to the MCU for a glue-less interface for proximity measurements.