The differential Hall Effect sensor SC9621 provides a high sensitivity and a superior stability over temperature and symmetrical thresholds in order to achieve a stable duty cycle. The integrated circuit is response to changing differential magnetic fields created by rotating ring magnets and by ferrous targets when coupled with a magnet. The device is particularly suitable for rotational speed detection and timing applications of ferromagnetic toothed wheels, such as, anti-lock braking systems, transmissions, crankshafts, etc.
The SC9621 sensor IC contains two integrated Hall transducers that are used to differentially respond to a magnetic field across the surface of the IC. The trigger switches the output off (output high) when the differential magnetic field crosses zero while increasing in strength (referred to positive direction), and switches the output on (output low) when the differential magnetic field crosses zero while decreasing (the negative direction).
The operation is achieved through the use of two separate comparators. Both comparators use the same reference point, 0 G, to provide high accuracy, but one comparator has a positive hysteresis, BHYS1, and the other a negative hysteresis, BHYS2. Therefore, one comparator switches (BOP) at the zero crossing on an increasing differential signal and the other switches (BRP) at the zero crossing on a decreasing differential signal. The hysteresis on each comparator precludes false switching on noise or target jitter.
The SC9621 can be exploited to detect toothed wheel rotation in a rough environment. Jolts against the toothed wheel and ripple have no influence on the output signal. Furthermore, the device can be operated in a two-wire as well as in a three wire-configuration.
The device is packaged in a 4-pin plastic SIP. It is lead (Pb) free, with 100% matte tin plated leadframe.