ATS645 Allegro MicroSystems, Inc., ATS645 Datasheet

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ATS645

Manufacturer Part Number
ATS645
Description
Ats645lsh True Zero Speed Miniature Gear-tooth Sensors
Manufacturer
Allegro MicroSystems, Inc.
Datasheet
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
• Large operating air gaps
• Automatic Gain Control (AGC)
Continued on the next page…
Packages: 4 pin SIP (suffix SH)
Not to scale
ATS645-DS, Rev. 3
range
Automatic Offset
Tracking
Control
DAC
Two-Wire True Zero Speed Miniature Differential
Amplifier
Hall
AOA DAC
Peak Hold
Functional Block Diagram
AGC DAC
Peak-Detecting Gear Tooth Sensor
Gain
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, the ATS645 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.
Continued on the next page…
Internal Regulator
Test Signals
ATS645LSH
VCC
GND
Test

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ATS645 Summary of contents

Page 1

... In addition, the ATS645 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. ...

Page 2

... The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006. These variants include: ATS645LSHTN-I2. 2 Contact Allegro for additional packing options. ...

Page 3

... Z CC CC(max) A Test conditions only ATS645LSH-I1 ATS645LSH-I2 ATS645LSH-I1 ATS645LSH-I2 / Ratio of high current to low current t > Target gear speed < 100 rpm R = 100 Ω LOAD LOAD Detecting Gear Tooth Sensor within specifi cation, unless otherwise noted 1 Min ...

Page 4

... ATS645LSH OPERATING CHARACTERISTICS (continued) using reference target 60-0, T Characteristic SWITCHPOINT CHARACTERISTICS Rotation Speed Analog Signal Bandwidth Operate Point Release Point CALIBRATION Initial Calibration DAC CHARACTERISTICS Allowable User-Induced Differential Offset 5 FUNCTIONAL CHARACTERISTICS Operational Air Gap Range 6 Maximum Operational Air Gap AG Range 7 Duty Cycle Variation ...

Page 5

... ATS645LSH REFERENCE TARGET, 60-0 (60 Tooth Target) Characteristics Symbol Outside Diameter D o Face Width F Circular Tooth Length t Circular Valley Length t v Tooth Whole Depth h t Material Reference Gear Magnetic Gradient Amplitude With Reference to Air Gap 800 700 600 500 400 300 200 100 0 0 ...

Page 6

... ATS645LSH Duty Cycle vs. Air Gap 100 RPM 0.5 1 1.5 Air Gap (mm) Duty Cycle vs. Air Gap 1000 RPM 0.5 1 1.5 Air Gap (mm) True Zero Speed Miniature Differential Peak- Characteristic Data I1 Trim (º -40 25 ...

Page 7

... ATS645LSH THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information CHARACTERISTIC Package Thermal Resistance *Additional information is available on the Allegro Web site. True Zero Speed Miniature Differential Peak- Detecting Gear Tooth Sensor Symbol TEST CONDITIONS* Single-layer PCB with copper limited to solder pads R Two-layer PCB with 3 ...

Page 8

... Figure 4: Voltages profi les for high side and low side two-wire sensing low I CC(High) (see fi gure 4). SENSE OUT VCC VCC ATS645 ATS645 GND GND OUT(L) R SENSE I+ I OUT V+ V OUT( OUT(H) Allegro MicroSystems, Inc. ...

Page 9

... ATS645LSH Automatic Gain Control (AGC) This feature allows the device to operate with an optimal internal electrical signal, regardless of the air gap (within the AG speci- fi cation). During calibration, the device determines the peak-to- peak amplitude of the signal generated by the target. The gain of the sensor is then automatically adjusted ...

Page 10

... Assembly Description 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 VCC ATS645 GND 4 Pins 2 and 3 floating ECU 100 Ω R SENSE , the device enters Reset, where the output state CC(UV) ...

Page 11

... When power (V > applied to the device, a short CC CCMIN 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 CC(High) Initial Offset Adjust The sensor intially cancels the effects of chip, magnet, and installation offsets ...

Page 12

... ATS645LSH The device must be operated below the maximum junction temperature of the device Under certain combinations of J(max) peak conditions, reliable operation may require derating sup- plied power or improving the heat dissipation properties of the application. This section presents a procedure for correlating factors affecting operating T ...

Page 13

... ATS645LSH 5.8 .228 5.0 .244 20.95 .825 13.05 .514 True Zero Speed Miniature Differential Peak- Detecting Gear Tooth Sensor Package SH Module 0.75 .0294 E 0.75 .0294 8.0 .315 2.9 .114 4.0 .157 A 1.7 .067 .039 0.6 .024 A 0.6 .024 Dimensions in millimeters. Untoleranced dimensions are nominal. U.S. Customary dimensions (in.) in brackets, for reference only ...

Page 14

... ATS645LSH True Zero Speed Miniature Differential Peak- Detecting Gear Tooth Sensor The products described herein are manufactured under one or more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283; 5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ...

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