ATS645LSHTN-I1 Allegro Microsystems Inc, ATS645LSHTN-I1 Datasheet - Page 9

• Manufacturer Part Number: ATS645LSHTN-I1
• Description: IC SENSOR GEAR TOOTH 4-SIP
• Manufacturer: Allegro Microsystems Inc
• Type: Special Purposer

Specifications of ATS645LSHTN-I1

• Sensing Range: 120mV Trip, 120mV Release
• Voltage - Supply: 4 V ~ 24 V
• Current - Supply: 8mA
• Output Type: Digital, Open Collector
• Features: Gear Tooth Type
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 4-SIP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Output (max): -

ATS645LSH
Figure 1. Relative motion of the target is detected by the dual Hall ele-
ments mounted on the Hall IC.
Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation
results in a low output signal when a tooth of the target gear is nearest
the face of the package (see fi gure 3). A right-to-left (pin 4 to pin 1) rota-
tion inverts the output signal polarity.
Hall Technology
The gear tooth sensor IC subassembly contains a single-chip
differential Hall effect sensor IC, an optimized samarium cobalt
pellet, and a fl at ferrous pole piece. The Hall IC supports two
Hall elements, which sense the magnetic profi le of the ferromag-
netic target simultaneously, but at different points (spaced at a
1.5 mm pitch), generating a differential internal analog voltage
(V
output signal.
The Hall IC is self-calibrating and also possesses a tempera-
ture compensated amplifi er 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 amplifi er design and the offset
rejection circuitry. The Hall transducers and signal processing
electronics are integrated on the same silicon substrate, using a
proprietary BiCMOS process.
Target Profiling
An operating device is capable of providing digital information
that is representative of the mechanical features on a rotating
target. The waveform diagram shown in fi gure 3 presents the
automatic translation of the mechanical profi le, through the mag-
netic profi le that it induces, to the digital output signal of the IC.
Hall Effect Device
PROC
Hall Element 2
Dual-Element
Target (Gear)
) that is processed for precise switching of the digital
Rotating Target
(Pin 4 Side)
South Pole
North Pole
1
4
True Zero Speed Miniature Differential Peak-
(Pin 1 Side)
(Concentrator)
Element Pitch
Hall Element 1
Hall IC
Pole Piece
Back-biasing
Rare-earth Pellet
Case
Branded Face
of Package
Functional Description
Output Polarity
Figure 3 shows the output polarity for the orientation of target
and package shown in fi gure 2. The target direction of rota-
tion shown is: perpendicular to the leads, across the face of the
device, from the pin 1 side to the pin 4 side. This results in the
IC output switching from high, I
leading edge of a tooth (a rising mechanical edge, as detected by
the IC) passes the package face. In this confi guration, the device
output current switches to its low polarity when a tooth is the
target feature nearest to the package. If the direction of rotation
is reversed, then the output polarity inverts.
Note that output voltage polarity is dependent on the position of
the sense resistor, R
Figure 3. Output Profi le of a ferrous target for the polarity indicated in
fi gure 2.
Figure 4: Voltages profi les for high side and low side two-wire sensing.
Detecting Gear Tooth Sensor IC
Target
Mechanical Profile
Representative
Differential
Magnetic Profile
IC Electrical
Output Profile, I
I
V
V
OUT
OUT(L)
OUT(H)
I+
V+
V+
OUT
SENSE
ATS645
GND
VCC
4
1
V
CC
(see fi gure 4).
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
V
R
I
OUT(L)
CC
SENSE
CC(High)
, to low I
ATS645
GND
VCC
4
1
V
CC
R
V
I
CC
OUT(H)
SENSE
CC(Low)
, as the
8