US1881ESE Melexis Inc, US1881ESE Datasheet - Page 27

• Manufacturer Part Number: US1881ESE
• Description: IC LATCH CMOS MP TSOT23-3
• Manufacturer: Melexis Inc
• Type: Bipolar Latchr

Specifications of US1881ESE

• Sensing Range: 9.5mT Trip, -9.5mT Release
• Voltage - Supply: 3.5 V ~ 24 V
• Current - Supply: 5mA
• Current - Output (max): 50mA
• Output Type: Digital, Open Drain
• Operating Temperature: -40°C ~ 85°C
• Package / Case: TSOT-23-3, TSOT-3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Other names: US1881ESETR

Biased Operation
Biased operation is a method of controlling the magnetic field surrounding a Hall IC and is quite similar
to the Push-Push Method. For example, if a South Pole were attached to the reverse side of a Hall Effect
Switch, the Hall IC would be held on the “OFF” position until a South pole of a larger magnitude is intro-
duced to the branded face of the sensor and cancels out the opposing magnetic flux. This can be a very
important concept if a Hall IC were located within an electronic system with other opposing magnetic
fields. It will ensure that the Hall Sensor cannot switch accidentally. Figure 11 is an example of the bias
method. In Figure 11, the push-button uses a bias magnet to ensure that the button is in the Off position
until being pressed. When the button is pressed, the magnet adjacent to the branded face moves in the
head-on configuration closer to the Hall IC. This positive flux density will cancel out the negative flux
density provided by the bias magnet, eventually turning the button ON. Once the button is released, the
two opposing South magnetic fields will repel each other and send the button to its original OFF position.
Figure 11, Push-button with Bias Magnet
If the US5881 Hall Effect Switch were tobe used in this bias magnet configuration, this switch would
N
N
S
S
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remain in the OFF position until the button is
pressed. If the magnet adjacent to the branded
face of the Hall IC has an air gap of 2.0mm before
being pressed, the switch will be exposed to a flux
density of approximately - 200Gauss. the button
will need to be moved a distance of 0.75mm
inward to exceed 250 Gauss and turn ON. After
being released, the magnets will repel and turn
OFF the Hall IC at a distance of 1.7 mm away
from the branded face.
Section 3 - Applications