The A3144 is an integrated Hall effect non-latching sensor. Holding a magnet near the sensor will cause the output pin to toggle. This makes for a robust presence sensor. A reed sensor also works nicely, but can be limited by the glass encapsulation and size. A hall effect sensor is much smaller, but can handle less current than a reed switch. The device includes an on-chip Hall voltage generator for magnetic sensing, a comparator that amplifies the Hall voltage, and a Schmitt trigger to provide switching hysteresis for noise rejection, and open-collector output. An internal bandgap regulator is used to provide temperature compensated supply voltage for internal circuits and allows a wide operating supply range. If a magnetic flux density larger than threshold Bop, the output is turned on (low). The output state is held until a magnetic flux density reversal falls below Brp causing the output to be turned off (high) (see datasheet bellow). Features: Superior Temp. Stability for Automotive or Industrial Applications 4.5 V to 24 V operation, works with most unregulated supplies Open-Collector 25 mA output, compatible with digital logic Reverse Battery Protection Activate with Small, Commercially Available Permanent Magnets Solid-State Reliability Small Size Resistant to Physical Stress