TLE4942, TLE4942C

TLE4942 - TLE4942C Data Sheet

February 2002

3

Functional Description

The differential Hall Effect IC detects the motion of ferromagnetic or permanent

magnet structures by measuring the differential flux density of the magnetic field. To

detect the motion of ferromagnetic objects the magnetic field must be provided by a

backbiasing permanent magnet. Either the South or North pole of the magnet can be

attached to the rear, unmarked side of the IC package.

Magnetic offsets of up to

± 20mT and mechanical offsets are cancelled out through a

self-calibration algorithm. Only a few transitions are necessary for the self-calibration

procedure. After the initial self-calibration sequence switching occurs when the input

signal crosses the arithmetic mean of its max. and min. values (e.g. zero-crossing for

sinusoidal signals).

The ON and OFF state of the IC are indicated by High and Low current

consumption. Each zero crossing of the magnetic input signal triggers an output

pulse.

I

Figure 3

Zero-crossing principle and corresponding output pulses

Differential

Magnetic Flux

Density

∆B

t

Range for EL pulse:

∆B

EL

Range for warning pulse:

∆B

Warning

∆B

Limit

(max .airgap

exceeded)

Figure 4

Definition of differential magnetic flux density ranges

Magnetic signal

Output Signal

Pulse length