Two-Wire, Differential, Vibration-Resistant Sensor
with Speed and Direction Output
ATS699LSN
FUNCTIONAL DESCRIPTION
Direction Detection
Sensing Technology
The sensor IC contains a single-chip Hall-effect circuit that sup-
ports a trio of Hall elements. These are used in differential pairs
to provide electrical signals containing information regarding
edge position and direction of target rotation. The ATS699 is
intended for use with ferromagnetic targets.
The sensor IC compares the relative phase of its two differential
channels to determine which direction the target is moving. The
relative switching order is used to determine the direction, which
is communicated through the output protocol.
Data Protocol Description
After proper power is applied to the sensor IC, it is capable of
providing digital information that is representative of the mag-
netic features of a rotating target. The waveform diagrams in
Figure 4 present the automatic translation of the target profiles,
through their induced magnetic profiles, to the digital output
signal of the sensor IC.
When a target passes in front of the device (opposite the branded
face of the package case), the ATS699 generates an output pulse
for each tooth of the target. Speed information is provided by the
output pulse rate, while direction of target rotation is provided by
the duration of the output pulses. The sensor IC can sense target
movement in both the forward and reverse directions.
FORWARD ROTATION
As shown in panel A in Figure 5, when the target is rotating
such that a tooth near the sensor IC—of -Fxxxx variant—passes
from pin 1 to pin 3, this is referred to as forward rotation. This
direction is opposite for the -Rxxxx variant. Forward rotation is
indicated by output pulse widths of tw(FWD) (45 μs typical).
REVERSE ROTATION
As shown in panel B in Figure 5, when the target is rotating such
that a tooth passes from pin 3 to pin 1, it is referred to as reverse
rotation for the -Fxxxx variant. Reverse rotation is indicated by
output pulse widths of tw(REV) (90 μs typical for -xxNxx variant,
or 180 μs typical for -xxWxx variant).
Pin 3
Pin 1
Panel A
Branded Face
of Package
Rotating Target
(Forward Rotation)
Pin 3
Pin 1
Panel B
Branded Face
of Package
Rotating Target
(Reverse Rotation)
Figure 4: Magnetic Profile
The magnetic profile reflects the features of the target, allowing
the sensor IC to present an accurate digital output(-xSxxx variant
shown).
Figure 5: Target Rotation (F Variant Shown)
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Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com