ATS684LSN datasheet(10/16 Pages) ALLEGRO

10 / 16 page

Two-Wire, Zero-Speed

Differential Gear Tooth Sensor IC

ATS684LSN

Allegro MicroSystems, LLC

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

(A) TEAG varying; cases such as

eccentric mount, out-of-round region,

normal operation position shift

(B) Internal analog signal, VPROC,

typically resulting in the IC

360

Target Rotation (°)

Hysteresis Band

(Delimited by switchpoints)

V+

magnetic field for digital output

V+

Larger

TEAG

Smaller

TEAG

Target

Larger

TEAG

Target

Smaller

TEAG

Smaller

TEAG

Figure 6: The Continuous Update Algorithm

Switchpoints are the threshold levels of the differential internal

analog signal (VPROC) at which the device changes output signal

state. The value of VPROC is directly proportional to the magnetic

flux density (B) induced by the target and sensed by the Hall

elements. As VPROC rises through a certain limit, referred to as

the operate point (BOP), the output state changes from ICC(Low) to

ICC(High). As VPROC falls below BOP to a certain limit, the release

point (BRP), the output state changes from ICC(High) to ICC(Low).

As shown in Figure 6, threshold levels for the switchpoints are

established as a function of the peak input signal levels. The

device incorporates an algorithm that continuously monitors the

input signal and updates the switching thresholds accordingly

with limited inward movement of VPROC. The switchpoint for

each edge is determined by the detection of the previous two

signal edges. In this manner, variations are tracked in real time.

Continuous Update of Switchpoints

The Continuous Update algorithm

allows the Allegro IC to interpret and

adapt to variances in the magnetic

field generated by the target as a

result of eccentric mounting of the

target, out-of-round target shape, and

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