6

30Dec03, Rev. 1.42

Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com

Allegro MicroSystems, Inc.

Self-Calibrating Gear Tooth Sensor with 9-Bit Signal Capture

ATS672LSB

POR. (Power-On Reset) Allows complete reset to the original

power-on state, when initial calibration occured, regardless of

the state of the device immediately prior to POR.

TC. (Temperature Coefficient) This supports fine tuning of the

ATS672 for flat parametric performance over the full rated oper-

ating temperature range.

Sensor Integration. The ATS672 contains a self-calibrating

Hall-effect IC that possesses temperature compensated amplifier

circuitry and a voltage regulator that provides supply noise rejec-

tion over the operating voltage range. The Hall transducer and

the electronics are integrated on the same silicon substrate using

a proprietary BiCMOS process. Changes in temperature do not

greatly affect this device due to the stable amplifier design and

the offset rejection circuitry.

Assembly Description. The ATS672 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.

Operation. When proper power is applied to the sensor, it is

capable of providing digital information that is representative

of the profile of a rotating gear. No additional optimization is

needed and minimal processing circuitry is required. This ease

of use should reduce design time and incremental assembly costs

for most applications.

Sensing Technology. The sensor contains a single-chip Hall-

effect sensor IC, a 4-pin leadframe, and a specially-designed rare

earth magnet. The Hall IC possesses a Hall element that mea-

sures the magnetic gradient created by the passing of a ferrous

object. The difference in the magnetic gradients created by a

tooth and valley allow the generation of the digital output signal.

The following output diagram corresponds to a sensor with the

standard polarity.

Functional Description

Sensing technology. As the target moves by the sensor, there is a change in the magnetic flux density, B, which is measured in

gauss (G). The left panel shows the effect of a tooth opposite the sensor, a higher B. The right panel shows the effect of a valley,

a lower B.

Ferrous Target

Magnetic Gradient

Digital Output Signal

Mechanical Profile