US5781LSE Melexis Inc, US5781LSE Datasheet - Page 20

• Manufacturer Part Number: US5781LSE
• Description: IC HALL EFFECT SWITCH TSOT-23
• Manufacturer: Melexis Inc
• Type: Unipolar Switchr

Specifications of US5781LSE

• Sensing Range: 15mT Trip, 3.5mT Release
• Voltage - Supply: 3.5 V ~ 24 V
• Current - Supply: 5mA
• Current - Output (max): 50mA
• Output Type: Digital, Open Drain
• Operating Temperature: -40°C ~ 150°C
• Package / Case: SOT-23
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Other names: US5781LSETR

Magnetic Design
Input Characteristics
Digital Hall-Effect Sensors have specific magnetic response characteristics that govern their actuation
from OFF to ON. These characteristics are classified in terms of operate point, release point and differ-
ential. The operate point, commonly referred to as BOP, is the point at which the magnetic flux density
turns the Hall Sensor ON, allowing current to flow from the output to ground. Conversely, the release
point, commonly referred to as BRP, is the point at which the magnetic flux density turns the Hall Sensor
OFF. The absolute difference between BOP and BRP is referred to as Hysteresis, Bhys. The purpose of
hysteresis is to eliminate false triggering, which can be caused by minor variations in input, electrical
noise and mechanical vibration. There are three basic types of Digital Hall Sensors commonly used, as
listed below:
Switch - (unipolar) Operates with a single magnetic pole. Guaranteed not to latch ON in the absence of
Latch - (bipolar) responds to both magnetic poles. Turns on in the presence of North or south pole, and
Bipolar Switch - (unipolar or bipolar) described as a device which responds to the zero-crossing from
The Hall-Effect Latch
The latch is a type of Hall IC which remains in either state (output ON or Off) until an opposite pole mag-
net is applied. A South magnetic pole turns the device ON (BOP). The device will stay ON until a North
magnetic pole is applied and turns it OFF (BRP). Melexis manufactures two types of Hall Effect latches.
designated for .2.2V to 18V operation. The US2880 series of Hall Effect Latches are designed for high
sensitivity. For more information refer to the data sheet section of this manual.
The Hall Effect Switch
There are two types of Hall Effect Switches, unipolar. The unipolar switch is normally “OFF” in the
absence of a magnetic field. The device turns ON (BOP) in the presence of a sufficiently strong South
magnetic pole, and turns OFF BRP) in the presence of a weaker South magnetic pole. MELEXIS manu-
factures the US5881UA and US5881SO Hall Effect Switches. For more information refer to the data sheet
section of this manual.
Magnetic Design Considerations
When designing a magnetic circuit, there are five considerations to be covered:
1. Cost of Hall IC, Magnet and Assembly
2. Temperature Range
3. Position Tolerance of Assembled Parts
4. Position Switching Accuracy
5. Tolerance Buildup
Section 3 - Applications
a magnetic field. Opposing field has no effect. Generally used for mechanical switch replace
ment.
turns off only when the opposing field is sufficiently strong. Guaranteed to latch. Used primary
ily in brushless DC motor applications.
North to South poles
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