3421 Datasheet, PDF (8/12 Pages) Allegro MicroSystems – HALL-EFFECT, DIRECTION-DETECTION SENSORS

3421 AND 3422
HALL-EFFECT,
DIRECTION-DETECTION
SENSORS
APPLICATIONS INFORMATION
Operation with Fine-Pitch Ring Magnets. For
targets with a circular pitch of less than 4 mm, a perfor-
mance improvement can be observed by rotating the front
face of the sensor subassembly (see below). This sensor
rotation decreases the effective sensor-to-sensor spacing,
provided that the Hall elements are not rotated beyond the
width of the target.
Applications. It is strongly recommended that an
external 0.01 µF bypass capacitor be connected (in close
proximity to the Hall sensor) between the supply and
ground of the device to reduce both external noise and
noise generated by the internal logic.
The simplest form of magnet that will operate these
devices is a ring magnet. Other methods of operation,
such as linear magnets, are possible. Extensive applica-
tions information on magnets and Hall-effect sensors is
also available in the “Hsall-Effect IC Applications Guide”
which can be found in the latest issue of the Allegro
MicroSystems Electronic Data Book, AMS-702 or Appli-
cation Note 27701, or at
www.allegromicro.com
0.059"
1.50 mm
A
1
2
3
4
5
α
TARGET FACE WIDTH, F
>1.50 SIN α (mm)
>0.059 SIN α (inch)
A
1
2
3
4
5
Rotated sensor for
fine-pitch ring
magnets
Dwg. MH-024
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]