US4881ESE Melexis Inc, US4881ESE Datasheet - Page 28

• Manufacturer Part Number: US4881ESE
• Description: IC HALL SW BIPO NORTH POLE SOT23
• Manufacturer: Melexis Inc
• Type: Bipolar Latchr

Specifications of US4881ESE

• Sensing Range: 6mT Trip, -6mT Release
• Voltage - Supply: 2.2 V ~ 18 V
• Current - Supply: 5mA
• Current - Output (max): 50mA
• Output Type: Digital, Open Drain
• Operating Temperature: -40°C ~ 85°C
• Package / Case: SOT-23
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Other names: US4881ESETR

Flux Concentrators
A flux concentrator, or pole piece, is a ferrous material used to significantly increase the performance of
a Hall Effect Sensor System. When a flux concentrator is placed opposite the pole face of a magnet, the
magnetic field channels through the concentrator, thereby increasing the flux density between the con-
centrator and the pole face.
Figure 13, Flux Concentrator
The reason this magnetic flux channels through the concentrator is because of the reluctance of the fer-
rous material. Reluctance is the resistance that magnetic flux lines experience as they flow from the North
pole into the South pole of a magnet. Ferromagnetic materials have lower reluctance than air, therefore a
pole piece provides an easier path for the flux to flow through, while increasing the flux density at the
same time. There are three benefits to adding a flux concentrator to a magnetic circuit. First, a less sensi-
tive Hall Effect Sensor can be implemented, a result of the increased flux density. The second benefit of
using a flux concentrator is that Hall Effect Sensor with a specific operate level can be actuated a greater
distance from the magnet, than if one were not in use. The addition of a pole piece also allows the use of
a magnet with a lower field intensity. A flux concentrator makes it possible to use a smaller magnet or a
magnet of different material to achieve the same operating characteristics as one with higher flux density
or a larger size. When choosing materials for a pole piece, pay attention to the following characteristics:
The permeability and reluctance of the material will affect its performance as a flux concentrator. Also,
pay close attention to the mechanical characteristics of machining and corrosion. These properties are
very important when selecting an alloy.
Concentrator
Ferrous
Magnet
3-9
N
S
Section 3 - Applications