Dual Output Differential

Speed and Direction Sensor IC

ATS605LSG

7

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Functional Description

Sensing Technology

The ATS605 module contains a single-chip, dual differential

Hall-effect sensor IC, a rare earth pellet, and a flat ferrous pole

piece (concentrator). As shown in Figure 4, the Hall IC supports

three Hall elements, which sense the magnetic profile of the

ferrous gear target simultaneously, but at different points (each

channel spaced at a 1.75 mm pitch), generating two differential

switching of the digital output signals.

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

ture compensated amplifier and offset cancellation 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

rejection circuitry. The Hall transducers and signal processing

electronics are integrated on the same silicon substrate, using a

proprietary BiCMOS process.

Target Profiling During Operation

An operating device is capable of providing digital information

that is representative of the mechanical features of a rotating gear.

The waveform diagram in Figure 4 presents the automatic trans-

lation of the mechanical profile, through the magnetic profile that

it induces, to the digital output signal of the ATS605. No addi-

tional optimization is needed and minimal processing circuitry is

required. This ease of use reduces design time and incremental

assembly costs for most applications.

Operating Modes:

Calibration

Once the power-on time has elapsed, the sensor IC internally

detects the magnetic profile of the target. The output becomes

active at the first detected switchpoint.

The gain of the sensor IC is adjusted during the Calibration

period, normalizing the internal signal amplitude for the air gap

range of the device. This Automatic Gain Control (AGC) feature

ensures that operational characteristics are isolated from the

effects of installation air gap variation.

Automatic Offset Adjustment (AOA) is circuitry that compen-

sates for the effects of chip, magnet, and installation offsets. (For

capability, see Allowable User-Induced Magnetic Offset, in the

Operating Characteristics table.) This circuitry works with the

range to allow for DAC acquisition of signal peaks.

Calibration also allows for the peak detecting DACs to properly

acquire the magnetic signal, so that Running Mode switchpoints

can be accurately computed.

Running Mode

After calibration is complete, direction information is available.

This information is communicated through the available output

option.

Peak-tracking DAC algorithms allow tracking of signal drift over

temperature changes, as well as tracking of target variations, such

as tooth-to-tooth variation and effective runout. The sensor’s

dynamic monitoring of these signal peaks is updated on each

tooth and valley edge.

Automatic Offset Adjust remains active, allowing the IC to com-

pensate for offsets induced by temperature variations over time.

Figure 3: Target Rotation for Default Sensing Configuration.

(A) Pin 4 to pin 1 is forward, and (B) pin 1 to pin 4 is reverse.