ATS612LSB_1 Datasheet, PDF (14/17 Pages) Allegro MicroSystems – Dynamic, Self-Calibrating, Peak-Detecting, Differential Hall Effect Gear Tooth Sensor

ATS612LSB
DYNAMIC, SELF-CALIBRATING, PEAK-DETECTING,
DIFFERENTIAL HALL-EFFECT GEAR-TOOTH SENSOR
APPLICATIONS INFORMATION — Continued
Operation with Fine-Pitch gears. For targets with a
circular pitch of less than 4mm, a performance improve-
ment can be observed by rotating the front face of the
sensor. This sensor rotation decreases the effective
sensor-to-sensor spacing and increases the capability of
detecting fine tooth or valley configurations, provided that
the Hall elements are not rotated beyond the width of the
target.
to pin 4), the output of the device will switch from LOW to
HIGH as the leading edge of the target passes the module,
which means that the output will be HIGH when the unit is
facing a tooth.
1
2
3
4
2.235 mm
0.088"
A
α
TARGET FACE WIDTH, F
>2.235 SIN α (mm)
>0.088 SIN α (inch)
Dwg. MH-018-1
Dwg. AH-006-1
Signal Timing Accuracy. The magnetic field profile width
is defined by the sensor element spacing and narrows in
degrees as the target diameter increases. This results in
improved timing accuracy performance for larger gear
diameters (for the same number of gear teeth).
Valley-to-tooth transistions will generally provide better
accuracy than tooth-to-valley transitions for large-tooth or
large-valley configurations. For highest accuracy, targets
greater than 100mm in diameter should be used.
Signal Duty Cycle. For repetitive target structures,
precise duty cycle is maintained over the operating air gap
and temperature range due to an extremely good symme-
try in the magnetic switch points and the internal self
calibration of the device. For irregular tooth geometries,
there will be a small but measureable change in pulse
width versus air gap.
Output Polarity. The output of the device will switch from
HIGH to LOW as the leading edge of the target passes the
module in the direction indicated below (pin 4 to pin 1),
which means that the output will be LOW when the unit is
facing a tooth. If rotation is in the opposite direction (pin 1
Power Supply Protection. The sensor contains an on-
chip voltage regulator and can operate over a wide supply
voltage range. For devices that need to operate from an
unregulated power supply, transient protection should be
added externally. For applications using a regulated
supply, external EMI/RFI protection is often required.
Insufficient protection can result in unexplained pulses on
the output line, providing inaccurate sensing information to
the user.
The filter capacitor and EMI protection circuitry can
easily be added to a PC board for use with these devices.
Provisions have been made for simple mounting of a
board on the back of the unit.
4
3
2
1
Dwg. AH-007
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