Two-Wire, Differential, Vibration-Resistant Sensor

with Speed and Direction Output

ATS699LSN

9

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

FUNCTIONAL DESCRIPTION

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.

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.

Pin 3

Pin 1

Rotating Target

(Forward Rotation)

Branded Face

of Package

Pin 3

Pin 1

Rotating Target

(Reverse Rotation)

Branded Face

of Package

Panel A

Panel B

Direction Detection

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

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

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

or 180 μs typical for -xxWxx variant).

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)