Miniature, Two-Wire, True Zero Speed

Differential Peak-Detecting Sensor IC

ATS682LSH

9

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Functional Description

Hall Technology

This single-chip differential Hall-effect sensor IC possesses

two Hall elements spaced at a fixed distance (1.5 mm), which

simultaneously are affected by the magnetic profile of the target,

processed for precise switching of the digital output signal.

The Hall IC is self-calibrating and also possesses a temperature

compensated amplifier and offset compensation 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 amplifier design and the offset

compensation circuitry. The Hall transducers and signal process-

ing electronics are integrated on the same silicon substrate, using

a proprietary BiCMOS process.

Target Profiling

An operating device is capable of providing digital informa-

tion that is representative of the magnetic features on a rotating

target. The waveform diagram shown in figure 3 represents the

automatic translation of the magnetic profile to the digital output

signal of the IC.

Output Polarity

Figure 3 shows the output polarity for the orientation of the target

and package shown in figure 2. The target direction of rotation

shown is perpendicular to the leads, across the face of the device,

from pin 1 to pin 4. This results in the IC output switching from

rising mechanical edge, as detected by the IC) passes the branded

face. In this configuration, the device output current switches to

its low polarity when a tooth is the target feature nearest to the

branded face. If the direction of rotation is reversed, then the

output polarity inverts.

Note: the translated output voltage polarity is dependent on the

Target (Gear)

Back-biasing

Rare-earthPellet

South Pole

North Pole

Case

(Pin 1 Side)

(Pin 4 Side)

Hall IC

Pole Piece

Element Pitch

(Concentrator)

Dual-Element

Hall Effect Device

Hall Element 1

Hall Element 2

of Package

Rotating Target

Branded Face

1

4

ATS682

VCC

GND

V

CC

I

CC

1

4

ATS682

VCC

GND

V

CC

1

4

I

CC

R

SENSE

R

SENSE

V+

V+

I+

Representative

Differential

Magnetic Profile

Target

Mechanical Profile

IC Electrical

Figure 1. Relative motion of the target is detected by the dual Hall

elements mounted on the Hall IC.

Figure 4. Voltage profiles for high-side and low-side two-wire sensing.

Figure 3. Output Profile of a gear target for the polarity indicated in figure 2.

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 Figure 3). A right-to-left (pin 4 to pin 1) rotation inverts

the output signal polarity.