Introduction
The function of a Hall sensor is based on the physical principle of the Hall
effect named after its discoverer E. H. Hall: It means that a voltage is
generated transversely to the current flow direction in an electric conductor
(the Hall voltage), if a magnetic field is applied perpendicularly to the
conductor. As the Hall effect is most pronounced in semiconductors, the most
suitable Hall element is a small platelet made of semiconductive material.
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The Hall effect: In a semiconductive platelet, the Hall voltage is generated
by the effect of an external magnetic field acting perpendicularly to the
direction of the current. |
In the Hall sensors made by Micronas the Hall element with its entire
evaluation circuitry is integrated on a single silicon chip. The chip is
produced using modern CMOS technology.
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CMOS Hall sensors made by Micronas in leaded and SMD package. The magnetic
flux component perpendicular to the chip surface is measured
(arrows). |
The Hall plate with the current terminals and the taps for the Hall voltage
are arranged on the surface of the crystal. This sensor element detects the
components of the magnetic flux perpendicular to the surface of the chip and
emits a proportional electrical signal which is processed in the evaluation
circuits integrated on the sensor chip.
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Functional principle of a Hall sensor: The output voltage of the sensor and
the switching state, respectively, depend on the magnetic flux density through
the Hall plate. |
The different types of Hall sensors are distinguished depending on the mode
of signal processing and signal output. Fundamentally, the sensors can be
divided into Hall Switches and linear Hall sensors.
Overview of Micronas’ sensor families
Hall switches
Hall switches (switching sensors) have an integrated comparator with
predefined switching points and a digital output which can be adapted to
different logic systems. All Hall switches include an open-drain output
transistor and require an external pull-up resistor to the supply voltage. A
standard Hall switch has a single Hall plate and responds to the absolute value
of the magnetic field perpendicular to the plate. The Hall switch is
characterized by the magnetic switching points BON (or BOP
) and BOFF (or BRPN). If the magnetic flux exceeds
BON , the output transistor is switched on; on dropping below
BOFF, the transistor is switched off. The magnetic hysteresis
BHYS is the difference between the switching points BON
and BOFF.
Definition of switching points
There are several types of Hall switches available which differ in their
switching points and behavior:
Latched switching sensors
The output turns low with the magnetic
south pole on the branded side of the package and turns high with the magnetic
north pole on the branded side. The output does not change if the magnetic field
is removed. For changing the output state, the opposite magnetic field polarity
must be applied.
Switching behavior of latched switching sensors
Bipolar switching sensors
The output turns low with the magnetic
south pole on the branded side of the package and turns high with the magnetic
north pole on the branded side. The output state is not defined for all sensors
if the magnetic field is removed. Some sensors will change the output state and
some sensors will not.
Switching behavior of bipolar switching sensor
Unipolar switching sensors
The output turns low with the magnetic
south pole on the branded side of the package and turns high if the magnetic
field is removed. The sensor does not respond to the magnetic north pole on the
branded side.
Switching behavior of unipolar switching sensors
Unipolar switching sensors with inverted output
The output turns
high with the magnetic south pole on the branded side of the package and turns
low if the magnetic field is removed. The output remains low with the magnetic
north pole on the branded side.
Switching behavior of unipolar switching sensors with inverted
output
Differential Hall switches
In addition to the standard switches described above, there are two special
versions of Hall switches available:
Differential Hall switches contain two
Hall plates which are about 2 mm apart from each other. The output transistor is
switched according to the difference of the magnetic flux
.B=B2–B1 between the plates. The output transistor is
switched on if the difference exceeds .BON and is switched off if the
difference drops below BOFF.
Two-wire Hall switches
These switches provide the output signal via their current consumption. They
employ an internal current source which is switched on or off depending on the
magnetic field at the Hall plate. Two-wire switches require only two connections
between sensor and evaluation circuit.
Output
signal of two-wire Hall switches
Linear Sensors
Linear Hall sensors generate an analog output voltage which is proportional
to the magnetic flux perpendicular through the Hall plate. The output
characteristic is defined by the parameters VOQ (output quiescent
voltage) and sensitivity.
Characteristics of linear Hall sensors
VOQ is the output voltage without a magnetic field (B = 0
mT).
Sensitivity is the ratio .VOUT/B
Offset compensation
Besides the Hall effect, there is a number of other voltage-generating
effects (e. g. mechanical package stress) which generate an offset to the Hall
voltage and can so impair the measuring accuracy of the sensors. With the active
offset compensation (chopper principle) applied for the first time by Micronas,
the direction of the current and the taps of the Hall voltage are continuously
commutated; this method allows the offset component to be suppressed. The result
is sensors with ultimate switching accuracy and temperature/long-term stability,
as well as low series scatter. Micronas’ CMOS Hall sensors are complete sensor
systems on a single chip. Apart from the actual Hall element, all circuits for
signal processing are integrated.
Micronas’ CMOS Hall sensors are complete sensor systems on a
single chip. The Hall element and all circuits for signal processing are
integrated.
All Hall switches belonging to the HAL 3xx, 5xx, 62x, 7xx, and HAL 1000
families, as well as the linear sensors HAL 8xx and HAL 401, are equipped with
active offset compensation.
Product Overview
Micronas offers nine families of Hall sensors which differ in terms of their
operating principle, switching behavior, and application-specific design. The
table shows the available sensor families and their essential
characteristics:
The table shows the available sensor families and their essential
characteristics:
1) Sensor output is connected to supply voltage. Therefore, a
short-circuit does not affect the sensor but might damage the external supply
voltage source.
Please note, that in addition to the sensor types listed, customer-specific
designs are possible. This could, e.g., be sensors that have specific switching
points, temperature compensation, or switching logic. Please contact us for
further details.
The CMOS Hall sensors made by Micronas have the following
characteristics: |
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Designed for the specifications and requirements of industry and automotive
electronics. |
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Most Hall switches operate in a wide supply voltage range (typical 4.5 V to
24 V, HAL 50x, HAL 51x, HAL 525, and HAL 535 from 3.8 V). The sensors are
available for different temperature ranges; they mainly operate in the ambient
temperature range –40 °C to 150 °C.
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Overview of CMOS Hall sensors by Micronas and their
applications: |
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HAL 114 and HAL 115: low-cost Hall switches
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HAL 300 and HAL 320: differential field sensors; HAL 300: optimized for
multi-pole ring applications; HAL 320: optimized for back-bias
applications.
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HAL 50x, HAL 51x, HAL 525, and HAL 525: allround family of Hall switches
comprising sensors with different magnetic switching points.
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HAL 556, HAL 566, HAL 57x, and HAL 58x: two-wire sensors supplying the
output signal via the current supply, thus saving one terminal in the system
design.
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HAL 62x: “low-jitter” Hall sensors with continuous signal processing,
delivering an output signal with a high degree of reproducibility. These sensors
are designed for the precise evaluation of very fast signals.
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HAL 7xx: special-purpose Hall sensors with two independent outputs for
controling position, speed, and direction of the target movement. These sensors
are designed for position-control applications with direction detection and
alternating magnetic signals such as multipole magnet applications, rotating
speed and direction measurement, position tracking, and window
lifters. |
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HAL 8xx: These linear sensors allow programming of the main characteristics
like magnetic field range, sensitivity, temperature compensation, and output
quiescent voltage in an internal EEPROM. By the electronic calibration of the
sensor in the final customer application, tolerances from the magnetic circuit
and mechanical assembly can be compensated. This TCOST (Total Compensation Of
System Toler-ances) principle eases the customer’s logistics, development, and
production. Programming is done by a supply voltage modulation. An
application tool (hard- and software) for easy calibration is available from
Micronas.
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HAL 1000: programmable Hall switch based on the HAL 8xx providing a swiching
output signal. The major characteristics – the two switching points
BON and BOFF – are programmable in the customer
application. |
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HAL 1500: programmable Hall switch. The major characteristics – offset,
hysteresis, output polarity and temperature coefficient – are programmable in
the customer application. The sensor also provides a multi-level switch output
and can be used as a linear sensor with low resolution (4 bit). The sensor is
programmed via its output pin by modulating the supply voltage. An application
tool (hard- and software) for easy calibration is available from
Micronas. |
Block
diagram HAL 855: Due to its integrated digital signal processing and the EEPROM
cells, this Hall sensor of the new generation is individually programmable.
Packages
The Hall switches 11x, 300, 320, 5xx, and 62x are available in the leaded
TO-92UA, as well, as in the SOT-89B SMD package.
The HAL 401 and HAL 7xx are
available in the SOT-89B SMD package, only.
The HAL 8xx and HAL 1000 are
available in the leaded package TO-92UT.