A dynamic differential Hall IC with current interface for automotive sensor applications

Magnetic sensors based on the Hall effect are gaining increasing importance for automotive applications. A vital field is the sensing of rotating target wheels for crankshaft, camshaft, gearbox or wheel speed detection. For reliable operation, magnetic differential fields ranging from /spl plusmn/60 mT down to approximately /spl plusmn/1 mT (that corresponds to a Hall voltage of 100 /spl mu/V) superimposed by homogenous fields of several 100 mT have to be resolved in an automotive environment. Major requirements are: Tj=-50/spl deg/C up to 210/spl deg/C, supplies between 4.5 V and approximately 30 V, immunity against supply ripple and radiated energy, and protection against reversed supply polarity. In the presented Hall IC, the magnetic field is sensed by two Hall probes spaced at 2.5 mm. The Hall signals are subtracted and amplified to feed a highpass filter including one external capacitor having a corner frequency of a few Hertz. A Schmitt-trigger comparator generates temperature-compensated thresholds. The chip is implemented in a standard bipolar technology.