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Sensing and Productivity Solutions

Magnetoresistive Sensor ICs

Standard Power Series: SM351RT, SM451R, SM353RT, SM453R

Figure 3. Alignment of the Magnet to the SOT-23 Package (SM351RT, SM353RT) Omnipolar Magnetoresistive Sensor IC

Ideal alignment: The magnet is aligned in the same plane as the sensor IC.

Offset alignment: The magnet is not aligned in the same plane as the sensor IC.

SM351RT,

SM353RT

Sensor IC

Magnet

Magnet movement

Magnet

SM351RT,

SM353RT

Sensor IC

Magnet movement

Magnet

The sensor IC detects the approaching magnet’s horizontal magnetic flux lines, turning the sensor IC to ON. The sensor IC stays

ON as the magnet continues to approach. When the magnet is located directly over the sensor IC, all magnetic flux lines are now

horizontal (see Figure 3.C). (Note: This alignment decreases the magnetic flux strength at the sensor IC.)

The magnetic flux lines stay horizontal as the magnet

Dead zones may occur when the majority of the magnet’s

magnetic flux lines become vertical as it approaches the

sensor IC, turning the sensor IC ON, then OFF, then ON

(see Figure 3.B).

Perpendicular magnet approach to the sensor IC eliminates possible dead zones.

Parallel magnet approach to the sensor IC may cause dead zones.

Figure 3.A

Figure 3.B

Figure 3.C

Magnet

SM351RT,

SM353RT

Sensor IC

Magnet movement

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