The A3423 incorporates two matched Hall elements to provide output signals that indicate the speed and direction of the target. The Hall elements are photolithographically aligned to within 1 µm. Maintaining accurate mechanical location between the two active Hall elements eliminates the major manufacturing hurdle encountered in fine-pitch detection applications.
The elements are spaced 1.63 mm apart, which is the optimal spacing to provide speed and direction information from small-geometry targets: typically ring magnets with a 3 mm pole width. Extremely low-drift amplifiers guarantee symmetry between the switches to maintain signal quadrature. An on-chip regulator allows use over a wide operating voltage range from 3.8 V to 24 V.
End-of-line trimming of the Hall-element switchpoints provides for tighter threshold tolerance and close matching between the elements. This results in a more precise duty cycle over the operating temperature range and air gap. The continuous-time method of offset cancellation delivers fast start-up and signal recognition as well as very low noise on the output.
Target applications are the sensing of motor speed and direction in automotive window-lift, sunroof, seat-position, power sliding door, windscreen wiper, transmission and differential systems, as well as industrial motors and drives.
The A3423 is initially available in a 4-lead SIP (suffix 'K') package, with a plastic 8-pin SOIC surface-mount version scheduled for Autumn 2007.