Worcester, Mass. Allegro MicroSystems, Inc. has added three new gear-tooth sensors to its line of AC-coupled Hall-effect devices that offer a smaller package size and an integrated filter capacitor to provide additional reliability. The new A1421LK, A1422LK, and A1423LK devices are suitable for use in speed, position and timing applications such as transmission and engine management, and can be used in industrial applications.
Each device includes a voltage regulator, two Hall-effect sensing elements, temperature-compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger, and an output driver that requires a pull-up resistor. The on-board regulator permits operation with supply voltages of 4.0 to 26.5 volts. The output stage can easily switch 20 mA over the full frequency response range of the sensor and is compatible with bipolar and MOS logic circuits.
However, to meet a variety of applications, the devices offer different switch points. The A1421 provides one zero crossing; the A1422 includes narrow set and symmetric switch points, and the A1423 offers high-vibration immunity with wide set switch points.
How they work: These gear-tooth sensors with monolithic integrated circuits switch in response to changing differential magnetic fields created by a moving ring magnet or by a ferrous target when back-biased with a magnet, and the two integrated Hall transducers sense changes in fields and are differentially amplified by on-chip electronics. Differential sensing provides immunity to radial vibration within the device's operating air gap range by rejection of the common mode signal change, said the company.
Steady-state system offsets are eliminated using an on-chip differential band-pass filter, which also provides relative immunity to interference from electromagnetic sources. The device uses advanced temperature compensation for the high-pass filter, sensitivity, and Schmitt trigger switch-points to guarantee optimal operation to low frequencies over a wide range of air gaps and temperatures, according to the company.
The devices are priced at $1.52 in quantities of 1,000. Delivery is 16 weeks.
Allegro MicroSystems, Inc., 1-508-853-5000 www.allegromicro.com