ATS660LSB

TRUE ZERO-SPEED,

HALL-EFFECT ADAPTIVE

GEAR-TOOTH SENSOR

www.allegromicro.com

11

APPLICATIONS INFORMATION — Continued

Dwg. MH-018-5 mm

A

2.2

α

TARGET FACE WIDTH, F

>2.2 SIN

α

Recommended evaluation technique. The self-

calibrating feature of the ATS660LSB requires that a

special evaluation technique be used to measure its high-

accuracy performance capabilities. Installation inaccura-

cies are calibrated out at power on; hence, it is extremely

important that the device be repowered at each air gap

when gathering duty cycle data.

The ATS660LSB is designed to minimize performance

variation (caused by the large air-gap variations resulting

from installation) by self-calibrating at power-on. These

functions should be tested using the procedures described

below.

Duty cycle capabilities after correct self-calibration can

be measured as follows:

1. Set the air gap to the desired value.

2. Power down and then power up the device.

3. Rotate the gear at the desired speed.

4. Wait for calibration to complete (64 output pulses to

occur).

5. Monitor output for correct switching and measure

accuracy.

6. Repeat the above for multiple air gaps within the

operating range of the device.

7. This can be repeated over the entire operating tem-

perature range.

There is an internal update algorithm that will maintain

the correct duty cycle as air gap changes with temperature.

Large changes in air gap will require the part to be reset

(by cycling power) to maintain the correct duty cycle.

Measurement of the effect of changing air gap after

power up:

1. Set the air gap to the desired value (nominal, for

example). Rotate the gear at the desired speed. Apply

power to the module. Wait for 64 output pulses to occur.

Monitor output for correct switching and measure accu-

racy.

2. Change the air gap by

±0.25 mm. Do not re-power the

module. Wait for update algorithm to finish adjusting

thresholds, typically 1 to 2 rotations on a 60-tooth gear.

Operation with fine-pitch gears. For targets with a

circular pitch of less than 4mm, a performance improve-

ment can be observed by rotating the front face of the

sensor. This sensor rotation decreases the effective

sensor-to-sensor spacing and increases the capability of

detecting fine tooth or valley configurations, provided that

the Hall elements are not rotated beyond the width of the

target.

Allegro