High Accuracy GMR Wheel Speed and Direction Sensor IC

A19350

9

Allegro MicroSystems, LLC

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

Calibration and Direction Validation

When power is applied to the A19350, the built-in algorithm per-

forms an initialization routine. For a short period after power-on,

the device calibrates itself and determines the direction of target

rotation. For the -xPx variant, the output transmits non-direction

pulses during calibration (Figure 12). For the -xBx variant, the

output does not transmit any pulses during calibration.

Once the calibration routine is complete, the A19350 will trans-

mit accurate speed and direction information.

Figure 12: Calibration Behavior of the -xPx Variant

Target Rotation

SS

NN

SS

NN

N

tor

W(FWD)

W(REV)

t

tor

W(FWD)

W(REV)

t

Target

Differential

Magnetic

Profile

t

Opposite

North Pole

Opposite

South Pole

Opposite

N→S Boundary

Opposite

S→N Boundary

Device Location at Power-On