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.

ATS645-DS, Rev. 3

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)

Two-Wire True Zero Speed Miniature Differential

Peak-Detecting Gear Tooth Sensor

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Functional Block Diagram

Not to scale

Packages: 4 pin SIP (suffix SH)

ATS645LSH

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VCC

Automatic Offset

Control

AOA DAC

Hall

Amplifier

AGC DAC

Gain

Tracking

DAC

Peak Hold

Internal Regulator

Test Signals

GND

Test