AD22157

PRELIMINARY TECHNICAL DATA Wheel Speed Sensor For ABS Systems Preliminary Technical Data FEATURES Speed and direction from 0Hz to 2500Hz Air gap diagnostics 2-wire current-loop operation Wide Operating Temperature Range Functional during temperature excursions to 190C Reverse Supply Protected (-30V) APPLICATIONS Automotive Wheel speed and direction sensing Transmission speed sensing Industrial Incremental position sensing Proximity switching Hall Array In Amps AD22157 Functional Block Diagram Vhigh Tracker 1 PWM 7mA 7mA Tracker 2 AD22157 Vlow GENERAL DESCRIPTION The AD22157 is a mixed signal magnetic field transducer designed for applications where both speed sensing and direction sensing of a ferrous target wheel are required over a wide speed range. The device operates from a 2 wire high compliance current loop and is suitable for continuous operation from -40C to 150C with supplies up to +20 Vdc. The sensor is designed to remain functional during voltage transients up to +27V. The sensor output format is a current pulse from 7mA to 14mA (the quiescent bias is 7mA) whose rising edge is accurately placed relative to the edges of the target wheel. The pulse width is determined by both target wheel direction and field strength. The output pulse is coded in multiples of a well defined time interval depending on direction and field strength in conformance with industry standards currently being promoted by leading systems manufacturers. Pulse widths corresponding to diff...