ATS674 Allegro MicroSystems, ATS674 Datasheet - Page 9

• Manufacturer Part Number: ATS674
• Description: (ATS673 / ATS674) Self-Calibrating TPOS Gear Tooth Sensor Optimized
• Manufacturer: Allegro MicroSystems

ATS673 and
ATS674
Assembly Description
The ATS673 and ATS674 true zero-speed gear tooth sensors
have a Hall IC-magnet configuration that is fully optimized
to provide digital detection of gear tooth edges. This sensor is
integrally molded into a plastic body that has been optimized for
size, ease of assembly, and manufacturability. High operating
temperature materials are used in all aspects of construction.
Sensing Technology
The gear tooth sensor contains a single-chip Hall effect sen-
sor IC, a 4-pin leadframe and a specially designed rare-earth
magnet. The Hall IC supports a Hall element that measures the
magnetic gradient created by the passing of a ferrous object. This
Figure 2. Device Cross Section. Motion of the target is detected by the Hall element mounted on the Hall IC. Panel A, the presence of a tooth feature on
the target is distinguished by a high magnetic flux density, B. Panel B, the presence of a valley feature is distinguished by its low magnetic flux density.
Figure 3. The magnetic profile reflects the geometry of the target, allowing the device to present an accurate digital output response.
Back-Biasing magnet
High-B field
Plastic
Hall IC
-LT Option
-HT Option
Self-Calibrating TPOS Gear Tooth Sensor Optimized
Target
Mechanical Profile
Target
Magnetic Profile
Sensor Output
Sensor Output
Sensor Output
Sensor Output
Switch State
Electrical Profile
Switch State
Electrical Profile
South Pole
North Pole
Operational Description
(A)
V
V
B
for Automotive Cam Sensing Applications
OUT
OUT
IN
V+
V+
B
0
Sensor Device
On Off On Off On Off On Off
Target (Gear)
Off
is illustrated in figure 2. The difference in the magnetic gradients
created by teeth and valleys allows the devices to generate a
digital output signal.
Output
After proper power is applied to the devices, they are then
capable of providing digital information that is representative of
the profile of a rotating gear, as illustrated in figure 3. No addi-
tional optimization is needed and minimal processing circuitry is
required. This ease of use reduces design time and incremental
assembly costs for most applications.
On Off On Off On Off On
(B)
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
(Concentrator)
Low-B field
Hall element
Leadframe
Pole piece
9