Dynamic, Self-Calibrating, Threshold-Detecting, Differential

Speed and Direction Hall-Effect Gear Tooth Sensor IC

ATS657

8

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

After the power-on time is complete, the ATS657 internally

detects the profile of the target. The output becomes active at the

first detected switchpoint. Figure 3 shows where the first output

pulse occurs for various starting target phases. After calibration is

complete, direction information is available and this information

is communicated through the output pulse width.

Figure 3. Start-up position effect on first device output switching

t

IC Output

Power-on

opposite valley

Power-on opposite

rising edge

Power-on opposite

falling edge

Power-on

opposite tooth

Target Differential

Magnetic Profile

Forward Target Rotation (Target passes from pin 4 to pin 1)

Device Location at Power-On

Tooth

Valley

Start-Up Detection