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PDF ATS645LSH Data sheet ( Hoja de datos )
| Número de pieza | ATS645LSH | |
| Descripción | True Zero Speed Miniature Gear Tooth Sensor | |
| Fabricantes | Allegro MicroSystems | |
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ATS645LSH
Two-Wire True Zero Speed Miniature Differential
Peak-Detecting Gear Tooth Sensor
Features and Benefits
• Fully optimized differential digital gear tooth sensor
• Single chip IC for high reliability
• Internal current regulator for 2-wire operation
• Small mechanical size (8 mm diameter x 5.5 mm depth)
• Air gap independent switchpoints
• Digital output representing gear profile
• Precise duty cycle signal over operating temperature
range
• Large operating air gaps
• Automatic Gain Control (AGC)
Continued on the next page…
Packages: 4 pin SIP (suffix SH)
Description
The components in speed sensing applications continue to
diminish in size to meet spatial constraints and weight reduction
requirements. As the geometries of gears become smaller, this
can compromise the capabilities of a gear speed sensor. The
ATS645 Hall-element-to-Hall-element spacing of only 1.5 mm
makes this device uniquely capable of accommodating very
fine-pitch gears. In addition, theATS645 signal peak-detecting
algorithm supports consistent switching at relatively large air
gaps, where the peak-to-peak amplitude is small.These features
make the ATS645 the ideal solution to detect the speed of fine-
pitch targets such as those found in ABS (antilock braking)
systems.
The ATS645 combines a Hall-effect sensing integrated circuit
and magnet to provide a manufacturer-friendly solution for true
zero-speed digital gear-tooth sensing in two-wire applications.
The device consists of a single-shot molded plastic package
that includes a samarium cobalt magnet, a pole piece, and a
Hall-effect integrated circuit that has been optimized to the
magnetic circuit. This small package can be easily assembled
and used in conjunction with a wide variety of gear shapes
and sizes.
Not to scale
Continued on the next page…
Functional Block Diagram
Hall
Amplifier
Automatic Offset
Control
AOA DAC
Tracking
DAC
Peak Hold
Gain
AGC DAC
Internal Regulator
Test Signals
VCC
GND
Test
ATS645-DS, Rev. 3
1 page  
ATS645LSH
True Zero Speed Miniature Differential Peak-
Detecting Gear Tooth Sensor
REFERENCE TARGET, 60-0 (60 Tooth Target)
Characteristics
Outside Diameter
Face Width
Circular Tooth Length
Circular Valley Length
Tooth Whole Depth
Material
Symbol
Do
F
t
tv
ht
Test Conditions
Outside diameter of target
Breadth of tooth, with respect
to sensor
Length of tooth, with respect
to sensor; measured at Do
Length of valley, with respect
to sensor; measured at Do
Low Carbon Steel
Typ.
120
6
3
3
3
–
Units
mm
mm
mm
mm
mm
–
Symbol Key
800
700
600
500
400
300
200
100
0
0.5
Reference Gear Magnetic Gradient Amplitude
With Reference to Air Gap
1 1.5 2 2.5
Air Gap (mm)
Branded Face
of Sensor
3 Reference Target
60-0
Reference Gear Magnetic Profile
Two Tooth-to-Valley Transitions
500
400
300
200
100
0
-100
-200
3.00 mm AG
-300
0.50 mm AG
-400
Air Gap
(mm)
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
-500
0 2 4 6 8 10 12
Gear Rotation (°)
*Differential B corresponds to the calculated difference in the magnetic field as
sensed simultaneously at the two Hall elements in the device (BDIFF = BE1 – BE2).
Allegro MicroSystems, Inc.
5
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
5 Page 
ATS645LSH
True Zero Speed Miniature Differential Peak-
Detecting Gear Tooth Sensor
SENSOR OPERATION
Each operating mode is described in detail below.
Power-On
When power (VCC > VCCMIN) is applied to the device, a short
period of time is required to power the various portions of the
IC. During this period, the ATS645 is guaranteed to power-on in
the high current state, ICC(High).
Initial Offset Adjust
The sensor intially cancels the effects of chip, magnet, and
installation offsets. Once offsets have been cancelled, the digital
tracking DAC is ready to track the signal and provide output
switching. The period of time required for both Power-On and
Initial Offset Adjust is defined as the Power-On Time.
Calibration Mode
The calibration mode allows the sensor to automatically select
the proper signal gain and continue to adjust for offsets. The
AGC is active, and selects the optimal signal gain based on the
amplitude of the VPROC signal. Following each adjustment to
the AGC DAC, the Offset DAC is also adjusted to ensure the
internal analog signal is properly centered.
During this mode, the tracking DAC is active and output switch-
ing occurs, but the duty cycle is not guaranteed to be within
specification.
Diagnostics
The regulated current output is configured for two wire appli-
cations, requiring one less wire for operation than do switches
with the more traditional open-collector output. Additionally,
the system designer inherently gains diagnostics because there
is always output current flowing, which should be in either of
two narrow ranges. Any current level not within these ranges
indicates a fault condition.
Running Mode
After the initial calibration period, CI, during which a signal
gain is established, the device moves to Running mode. During
Running mode, the sensor tracks the input signal and gives an
output edge for every peak of the signal. AOA remains active to
compensate for any offset drift over time.
Allegro MicroSystems, Inc.
11
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet ATS645LSH.PDF ] | |
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