Hall IC knowledge explanation

Date：2019-09-18 15:08:28 Browse：405

Hall IC is a product of Hall element and electronic circuit. It is made by Hall element, amplifier, temperature compensation circuit and voltage regulator circuit using integrated circuit technology. It can sense all physical quantities related to magnetism and output related electronic control information. Therefore, Hall IC is both an integrated circuit and a magnetic sensor. It is generally available in DIP or flat package.

1. The principle of Hall IC

When a piece of energized semiconductor wafer is placed vertically in a magnetic field, a potential difference is generated on both sides of the sheet, which is called a Hall effect. This potential difference is called the Hall potential, and the magnitude of the potential is E = KIB / d, where K is the Hall coefficient, d is the thickness of the sheet, I is the current, and B is the magnetic induction. The principle of the Hall effect: In a three-dimensional space, the Hall semiconductor plate is in the XOY plane, which is perpendicular to the direction of the magnetic field, the magnetic field is directed to the direction of the Y axis, and the current I is passed along the X axis, due to the interaction of the moving charge and the magnetic field. As a result, a Hall potential E is generated in the Z-axis direction, and the value is generally up to several tens of millivolts. For this reason, the Hall element and the electronic circuit are integrated on a silicon substrate of about 2 mm*2 mm, and a Hall IC with good temperature stability and high reliability is formed.

2. The classification of Hall IC

Shown according to the nature of the output signal. As shown in FIG. 9, a linear type Hall integrated circuit can obtain an output voltage proportional to the strength of the magnetic field. Although the sensitivity of the magnetic field can be adjusted by the amplification of the circuit, the ratio range is narrowed at high sensitivity (although the power supply 5V makes the sensitivity reach 10mV/Oe, the ratio ranges below 500Oe).

The switch-type Hall IC can obtain the ON-OFF voltage in a certain range of magnetic fields. The hysteresis phenomenon of the switch type to the magnetic field is to make the switching action more accurate for the Hall integrated circuit linear type. Deliberately designed this way.

It can also be classified according to the manufacturing method. Although any of the manufacturing methods can obtain the same characteristics, in the present stage, the bipolar Hall integrated circuit has begun to enter the stage of commercialization.

3. The application of Hall IC

Hall IC has the characteristics of no contact, no wear, no spark, low power consumption, long life, high sensitivity and high operating frequency. It can work reliably and stably in various harsh environments. For switching Hall ICs, the most basic application is as a proximity switch, such as Hall contactless switches, limit switches, direction switches, pressure switches, tachometers, etc.; linear Hall ICs are available. Non-contact ranging, non-contact potentiometer, brushless motor, Gauss meter for magnetic field measurement, magnetic flaw detection, etc.

For the switching Hall IC, the output terminal is usually in the form of an open collector transistor or an open emitter emitter, so it can be easily connected to various loads, such as direct drive transistor, LED, optocoupler, single Two-way thyristors and small current relays, and can interface with TTL and CMOS digital circuits, PLC input ports, solid state relays, and various AC and DC electronic switches.

4. The considerations of Hall IC

1) The operating voltage range of the Hall IC is wide, but the voltage should be low and low in practical use. Generally, it is suitable at 4.5-6V. Excessive power supply voltage will cause the temperature rise of the circuit and the circuit will be unstable.

2) When the switching Hall IC drives the load, its load current should be less than the load capacity of the Hall IC. In order to make the Hall's output voltage amplitude large, a load resistor with a larger resistance is generally added to the output terminal.

3) When the load capacity of the Hall IC drive is inductive, a freewheeling diode should be added to the output.

4) It is better to add isolation and buffer stages when driving loads of different levels than Hall ICs. Optocouplers or triode driver stages can be used.

5) When transmitting the Hall IC signal over a long distance, a decoupling capacitor can be added between the switch output and ground to eliminate the interference pulse; the output signal of the linear Hall IC should be transmitted using the coaxial cable, but the longest is not allowed. More than tens of meters.

6) The magnetic sensing distance of most Hall ICs is 5-10 mm. It must be controlled in practical use, and the transmitting magnet should be placed opposite to the sensing point of the Hall IC to reduce the magnetic resistance of the magnetic circuit. The letter and detection are reliable and accurate.

7) In order to enhance the magnetic induction sensitivity of the switch or linear Hall IC, it is also possible to use a small magnetic steel to enhance the magnetic bias or increase the area of the magnetic steel.

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