ATS616LSG Allegro MicroSystems, ATS616LSG Datasheet - Page 9

• Manufacturer Part Number: ATS616LSG
• Description: Dynamic Self-Calibrating Peak-Detecting Differential Hall Effect Gear Tooth Sensor
• Manufacturer: Allegro MicroSystems

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Assembly Description.
Hall IC/magnet configuration that is fully optimized to provide
digital detection of gear tooth edges. This sensor is packaged in
a molded miniature plastic body that has been optimized for size,
ease of assembly, and manufacturability. High operating tem-
perature materials are used in all aspects of construction.
After proper power is applied to the component, the sensor is
capable of instantly providing digital information that is repre-
sentative of the profile of a rotating gear. No additional optimi-
zation or processing circuitry is required. This ease of use should
reduce design time and incremental assembly costs for most
applications.
Sensing Technology.
single-chip differential Hall effect sensor IC, a samarium cobalt
magnet, and a flat ferrous pole piece (figure 2). The Hall IC
consists of 2 Hall elements (spaced 2.2 mm apart) located so
as to measure the magnetic gradient created by the passing of a
ferrous object. The two elements measure the magnetic gradient
and convert it to an analog voltage that is then processed in order
to provide a digital output signal.
The Hall IC is self-calibrating and also possesses a tempera-
ture compensated amplifier and offset cancellation circuitry. Its
voltage regulator provides supply noise rejection throughout the
operating voltage range. Changes in temperature do not greatly
affect this device due to the stable amplifier design and the offset
Figure 2. Relative motion of the target is detected by the dual Hall ele-
ments mounted on the Hall IC.
ATS616LSG-DS, Rev. 1
Hall Effect Device
Dynamic Self-Calibrating Peak-Detecting Differential Hall Effect Gear Tooth Sensor
Hall Element 2
Dual-Element
Target (Gear)
(Pin n >1 Side)
The gear tooth sensor module contains a
The ATS616 gear-tooth sensor is a
South Pole
North Pole
(Pin 1 Side)
(Concentrator)
Element Pitch
Hall Element 1
Hall IC
Pole Piece
Back-biasing Magnet
Case
Functional Description
ATS616LSG
rejection circuitry. The Hall transducers and signal processing
electronics are integrated on the same silicon substrate, using a
proprietary BiCMOS process.
Internal Electronics.
peak detection scheme to eliminate magnet and system offsets.
This technique allows dynamic coupling and filtering of offsets
without the power-up and settling time disadvantages of classical
high-pass filtering schemes. The peak signal of every tooth and
valley is detected by the filter and is used to provide an instant
reference for the operate and release point comparator. In this
manner, the thresholds are adapted and referenced to individual
signal peaks and valleys, providing immunity to zero line varia-
tion from installation inaccuracies (tilt, rotation, and off-center
placement), as well as for variations caused by target and shaft
eccentricities. The peak detection concept also allows extremely
low speed operation for small value filter capacitors.
The ATS616 also includes self-calibration circuitry that is
engaged at power on. The signal amplitude is measured, and
then the device gain is normalized. In this manner switchpoint
drift versus air gap is minimized, and excellent timing accuracy
can be achieved.
The AGC (Automatic Gain Control) circuitry, in conjunction
with a unique hysteresis circuit, also eliminates the effect of
gear edge overshoot as well as increases the immunity to false
switching caused by gear tooth anomalies at close air gaps. The
Differential
Magnetic Flux
Figure 3. The peaks in the resulting differential signal are used to set the
operate, B
Device Output
V
OUT
V
OUT(sat)
V
OP
B+
0
B–
CC
, and release, B
The processing circuit uses a patented
RP
, switchpoints.
Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
www.allegromicro.com
B
OP
B
RP
B
OP
B
RP
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