ASIL-Compliant Hall-Effect Wheel Speed Sensor IC

with Speed and Direction Output

A19300

10

Allegro MicroSystems

955 Perimeter Road

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

www.allegromicro.com

FUNCTIONAL DESCRIPTION

The A19300 sensor IC contains a single-chip Hall-effect circuit

that supports three Hall elements. These elements are used in

differential pairs to provide electrical signals containing informa-

tion regarding edge position and direction of target rotation. The

A19300 is intended for use with ring magnet targets, or, when

back-biased with an appropriate magnet, with ferrous targets. The

IC detects the peaks of the magnetic signals and sets dynamic

thresholds based on these detected signals.

Data Protocol Description

When a target passes in front of the device (opposite the branded

face of the package case), the A19300 generates an output pulse

for each magnetic pole or for each tooth and each valley of the

target. Speed information is provided by the output pulse rate,

while direction of target rotation is provided by the duration of

the output pulses.

FORWARD ROTATION

For the –F variant, when the target is rotating such that a target

feature passes from pin 1 to pin 2, this is referred to as forward

rotation. This direction of rotation is indicated on the output by

a tW(FWD) pulse width. For the –R variant, forward direction is

indicated for target rotation from pin 2 to 1 (refer to Figure 7).

REVERSE ROTATION

For the –F variant, when the target is rotating such that a target

feature passes from pin 2 to pin 1, this is referred to as reverse

rotation. This direction of rotation is indicated on the output by

a tW(REV) pulse width. For the –R variant, reverse direction is

indicated for target rotation from pin 1 to 2.

Output edges are triggered by BDIFF transitions through the

switch points. On a crossing, the output is first set to ICC(LOW) for

a duration of tw(PRE), after which the output pulse of ICC(HIGH) is

present for tw(FWD), tw(REV), or tw(WARN). The IC is always capa-

ble of properly detecting input signals up to the defined operating

frequency. The tw(PRE) period is dominant, thus always providing

rising output edge, but at high frequencies potentially truncating

the ICC(HIGH) duration.

Figure 7: Target Orientation Relative to Device

(ring magnet shown).

N

N

N

N

N

S

S

S

S

S

N

N

N

N

N

S

S

S

S

S

(A) Forward Rotation (-F variant)

(B) Reverse Rotation (-F variant)

Branded Face

of Sensor

Branded Face

of Sensor

Pin 1

Pin 2

Pin 1

Pin 2

Rotating Target

Rotating Target

Figure 8: Output Timing Example

S

N

tw(FWD)

tw(FWD)

tw(PRE)

tw(PRE)

ICC(LOW)

ICC(HIGH)