Magnetic hall effect based sensors final

Magnetic-Hall effect Based
Sensors

Sanjay Jagarwal
B.Tech Chemical 3rd year

Hall effect

The Hall effect is the production of a voltage difference (the Hall
voltage) across an electrical conductor, transverse to an electric
current in the conductor and a magnetic field perpendicular to
the current.

Discovered by Edwin Hall in 1879.

Hall effect
Lorentz Force:
F = q[E + (v x B)]

•Hall voltage is produced by charge accumulation on sidewalls.
•Charge accumulation balances Lorentz Force.
•Charge accumulation increases resistance.

Typical Shapes of Hall Sensors:
Hall plate area should be small. To accuratly measure magnetic
flux density, Hall plate area should be smaller than cross section
of field being measured.
Transverse (useful when fields must be measured in thin gaps.)
Can be as small as .006”

Axial (useful when field is parraellel to axis of hole. Traveiling wave tubes or solenoids.)
Can be as small as .063” in diameter.

Hall voltage
For simple conductors;

IB IB
VH RH
ned d
Where n = carrier density, d = conductor length
• RH is known as the Hall coefficient

• VH α B  Useful for measuring B-Fields

Gaussmeter Probe uses a hall sensor

Hall coefficient
• The Hall coefficient is the ratio of the induced electric field to
the product of the current density and the applied magnetic
field.

• It is a characteristic of the material from which the conductor
is made.

• The value of Hall coefficient depends on the
type, number, and properties of the charge carriers that
constitute the current.

Hall effect type
• Magnetic Hall effect

• Quantum Hall effect

• Spin Hall effect

• Quantum spin Hall effect

• Anomalous Hall effect

Magnetic Hall effect sensors

• A Hall Effect sensor is a transducer which varies its output
voltage in reaction to a magnetic field.
• These type of sensors are used for proximity switching, speed
detection, positioning and current sensing applications.
• The sensor operates like an analog transducer, thus directly
returning a voltage.
• Its distance from the Hall plate can be determined with a
known magnetic field.

Hall effect magnetic proximity sensor IC

• By using groups of Hall Effect sensors, the relative position of
the magnet can be determined.
• The electricity which is carried through a conductor will
produce a magnetic field which varies according to the current.
• The sensor can be used in order to measure the current
without interrupting the circuit.
• The sensor is typically integrated with a permanent magnet or a
wound core that surrounds the conductor to be measured.

Hall probe

Pira DCS # 5M10.10
Equipment:
Magnet Hall Probe Ballistic Galvanometer
6V Battery Wires

• A Hall probe contains an indium compound semiconductor
crystal such as indium antimonide, mounted on an aluminum
backing plate, and encapsulated in the probe head.
• The plane of the crystal is perpendicular to the probe handle.
• Connecting leads from the crystal are brought down through
the handle to the circuit box.

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 (Latched, Unipolar, Bipolar,
Unipolar with inverted output, etc.).

• 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 can respond 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; if it drops below BOFF, the
transistor is switched off. The magnetic hysteresis BHYS is the
difference between the switching points BON and BOFF.

Hall Sensor System overview
Switch/Latch Hall sensor
Linear Hall sensor

FRONT END BACK END

Input Input Signal Output OUTPUT
LPF Comparator
switches amp recovery amp INTERFACE

Most of the offset, noise and
sensitivity problems are here!!!

How we reduce Hall cell offset ?

Static Techniques (QUADS) Dynamic Techniques (current spinnig)

+ - + -

- + - +
+ - Phase 0 Phase 90

- +
Current spinning
QUADS
• CELL Offset is spatially averaged, thus
Offset from each single toalmostbe as high
Cell offset reduced cell can zero
Cell offset reduced to +/- 100uv
highly reduced as 10mv!!!
• Residual offset depends on individual
offset contribution mismatches

How we reduce Hall cell noise ?

Current driving (CD) Voltage driving (VD)

- At room temp SNR is worse than VD -At room temp SNR is better than CD
- At 150C is the same as VD -At 150C is the same as CD
- Sensitivity linearity over temp is -Sensitivity over temp is parabolic
better

rn VH rn
S SI I H S SI
q t Nd RH q t N d

How we reduce INPUT AMPLIFIER offset ?

Residual offset of chopping….how we reduce it?

Some results from the actual world - offset
CHOPPER-STABILIZED AMP Residual OFF=F(fck)
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5
700

DC
OFFSET
600
VSH IS
ON
500

Output referred (G=115x)
400

Res off ][mv]
300

200

100

0
100 200 400 600 800 1000
freq [KHz]

Some results from the actual world – ripple
Ripple (modulated offset)
1MHz 800KHz 600KHz

400KHz 200KHz 100KHz

Some results from the actual world – noise (1)
1/f reduction
INPUT
CHOPPER POST-CH
FLICKER
NOISE LPF
f fCK f

fk ~ 2KHz

~ 90nv/ Hz

However…
• How do we ADD amplifier + Hall Cell offsets ?
• What freq do we chop at ?
• What about noise modulation ?
• What about the LPF recovery system ?
– Is it too large ? Too much delay ?

•  For many years Patented technique SH RECOVERY was
used.
• NO LPF (but Sinc Filter) , No delay.  but Aliasing Noise.

• Just now new ideas are being developed to use Topologies
that combine no LPF with low noise amplifiers (aliasing free).

Chopper with SH Recovery
First DOC FE improvement: SH RECOVERY chopper (1995 – DB2)
Goal was to obtain a relaxed LPF, with small area and delay

OSR f CK / f 3dB
BW 1- pole (OSR 10)
H 5
f CK

A LPF

Demodulation
+ S&H

Vsig Vsig
Vsig
Voff Voff
Voff

Results of experiments:
- Hall cell : Current spinning allows to separate Hall cell offset from signal  offset or
signal could be modulated (chopped)
- Input Amplifier:
- Chopping is the most suited DOC technique for high accuracy (low offset, low
noise) systems
+ Totally removes 1/f noise and offset
- Limits amplifier bandwidth
- SH RECOVERY
+ Helps reduce delay with small area
- Introduces aliasing
- Hall Cell and Amplifier offset can be added in the base band while the signal is
modulated.

We have the signal … now what ?
• Offset was reduced, Gain stabilized over temp… what else ?

• Process Variations & Application errors  Trimming.
– Needs to be NON-VOLATILE memory.  Poly fuses.
• Bank of fuses to affect analog parameters (Gain, Sens, etc)
• Can also be EEprom … but 150C is a problem.

• Output the signal  What format ?
– Binary (H or L)… if B>Bop , Vout = L or B<Brp , Vout = H // Bop-Brp=Bhy
– Linear … requires output amplifier (class A or AB), Ro < 10ohm.
– Digitized , need a AD converter. High resolution (12bit)… sigma-delta.

Application of Hall effect based
sensors
• Hall Effect Switches
Unipolar Switches
Bipolar Switches
• Hall Effect Fan Motor Drivers
• Hall Effect Latches
• Linear Hall ICs
• Special-Purpose Hall ICs
• Triaxis® Hall ICs

Hall Effect Switches
MLX92241
The device integrates a voltage regulator, Hall sensor with advanced offset cancellation system,
programmable digital logic and a current sink-configured output driver, all in a single package.
Uses:
-Bop
- Brp
- Hysteresis
- Temperature Compensation
- Active Pole
- Output Polarity
Features and Benefits:
• MLX92241 Features and Benefits
• Wide operating voltage range: from 2.7V to 24V
• Very wide range for magnetic sensitivity
• Chopper-stabilized amplifier stage
• Programmable negative temperature coefficient
• Reverse Supply Voltage Protection
• Under-Voltage Lockout Protection
• Thermal Protection
• High ESD rating / Excellent EMC performance
• Thin SOT23 3L Green Compliant package
• Factory Programmable magnetic switching thresholds (Bop, Hyst, TC)

Hall Effect Unipolar Switches
MLX92221
The device integrates a voltage regulator, Hall sensor with advanced offset cancellation
system, programmable digital logic and a current sink-configured output driver, all in a
single package.
Uses:
-Bop
- Brp
- Hysteresis
- Active Pole
- Output Polarity

Hall Effect Unipolar Switches
MLX92241
The device integrates a voltage regulator, Hall sensor with advanced offset cancellation
system, programmable digital logic and a current sink-configured output driver, all in a
single package.
Uses:
-Bop
- Brp
- Hysteresis
- Active Pole
- Output Polarity

Hall Effect Bipolar Switches
US2881
The device integrates a voltage regulator, Hall sensor with dynamic offset cancellation
system, Schmitt trigger and an open-drain output driver, all in a single package.
-The device is delivered in a Thin Small Outline Transistor (TSOT) for surface
mount process and in a Plastic Single In Line (TO-92 flat) for through-hole
mount.
-Both 3-lead packages are RoHS compliant.

• Wide operating voltage range from 3.5V to 24V
• Very high magnetic sensitivity
• CMOS technology
• Low current consumption
• Open drain output
• Thin SOT23 3L and flat TO-92 3L both RoHS Compliant packages
• SE package North Pole Active
• UA package South Pole Active

Hall Effect Fan Motor Drivers
MLX90283
The MLX90283 is a one-chip solution for driving single-coil brushless DC vibration motors.

Designed in mixed signal CMOS technology, the device integrates Hall sensor with dynamic
offset cancellation, control logic and full bridge output driver.

The device is delivered in an Ultra Thin QFN package. Its 0.4mm thickness enables thin and
competitive vibration motor design.
This 6-pin leadless package is RoHS compliant.
• Low supply voltage: 1.8V ~ 3.6V
• Active Start (proprietary design to address Dead Point issue)
• High motor efficiency
• High sensitivity Hall sensor
• Full Bridge output driver
• Reverse voltage protection
• Ultra thin leadless RoHS compliant package
• No external components

MLX90285
The MLX90285 is a really cool driving solution for silent brushless cooling fans. It provides a
robust, high performance and fully integrated Hall effect based fan driver IC, including
technology lowering both acoustic and electrical noise. This device is ready to serve demanding
cooling requirements in office equipment or consumer electronics such as Laser
Printers, Projectors or Flat-Screen Televisions.

• 2-coil fan driver
• Wide Operating Voltage range: from 5V to 24V
• 1-chip solution: Hall element + Output Drivers
• Soft Switching for Low Noise : Acoustic & Electrical
• Active Slope Control without external components
• - automatically adapts slope to rotation speed
• Two-Stage Thermal Protection
• Locked Rotor Protection and auto-restart
• Output options:
• - Tachometer open drain output (MLX90285-FG)
• - Alarm open drain output (MLX90285-RD)
• “Green” Compliant Package options:
• - Available in 4-pin through-hole VK (“No-VDD” design)
• - surface mount SOIC8
• Pin-to-pin compatible with US90A & US91A

US168
The use of Melexis Soft Switching concept lowers the acoustic and electrical motor noise
and provides smoother operation.
The device is also provided in a Chip Scale Package, the smallest packaged IC configuration
available. The CSP saves valuable PCB and housing space allowing smaller integration. The
footprint of the new Ultra-Thin QFN (Quad Flat No leads) package is only 3mm2 (1.5 x
2mm) with 0.43mm maximum thickness.
• Soft switching for low noise
• Low supply voltage: 1.8V to 6.5V
• Full bridge driver
• High sensitivity integrated Hall sensor
• Low power consumption
• Reverse voltage protection
• Locked rotor protection and auto-restart
• Thermal protection and auto-restart
• No external components needed
• Tachometer output signal (FG)
• Thin SOT23-5L RoHS compliant package
• Ultra thin leadless UTQFN-6L RoHS compliant package.

Hall Effect Two-Coil Fan Motor Drivers
US890
Based on the advanced Melexis CMOS process, the IC contains a Hall-effect sensor, dynamic
offset correction and powerful output drivers with 1200mA peak output current capability.
Specially designed for driving large fans, the device is optimized for low start-up voltage.
The Frequency Generator open-drain output makes easier the connectivity with any
external interface such as hardware monitoring or Super I/O IC.

• Peak output current up to 1200mA
• Low start-up voltage
• Low output resistance
• High sensitivity integrated Hall Sensor
• Power-efficient CMOS and power MOSFETs
• Built-in output protection clamping diode
• Locked rotor protection and auto-restart
• Integrated tachometer signal protected output
• Low cost
• 2-coil fan driver with FG output in
• RoHS Compliant 4-pin VK package

Hall Effect Latches
US890
The MLX90224 series are dual Hall effect latches. It includes two Hall effect latch
functions of which typical thresholds are +/- 2.0 mT. In each latch, the magnetic flux
detection is performed by
a switched silicon Hall plate.
The BOP and BRP are temperature-compensated and give a sensitivity temperature
coefficient of 500 ppm/oC to compensate popular magnets.
The output will be latched off (BRP) in the presence of a
North field. Spacing on the plates is 1.85mm. The MLX90224 B series are designed for
direction detection with a high speed chopper which provides 15ms delay.
• Chopper Stabilized Amplifier Stage
• CMOS for Optimum Stability, Quality and Cost
• Dual Output 4.5V to 26V Operation
• Phase/Direction Detection (B)
•

Hall Effect Latche- Low Voltage & High
Sensitivity
US3881
The device integrates a voltage regulator, Hall sensor with dynamic offset
cancellation system, Schmitt trigger and an open-drain output driver, all in a single
package.
The low operating voltage and extended choice of temperature range make it
suitable for use in automotive, industrial and consumer low voltage applications.
The devices are delivered in a Thin Small Outline Transistor (TSOT) for surface
mount process and in a Plastic Single In Line (TO-92 flat) for through-hole mount.
Both 3-lead packages are RoHS compliant.
• Features and Benefits:
• Operating voltage range from 2.2V to 18V
• High magnetic sensitivity – Multi-purpose
• CMOS technology
• Open drain output
• Thin SOT23 3L and flat TO-92 3L both RoHS Compliant packages
• SE package North Pole Active
• UA package South Pole Active

Linear Hall ICs
MLX90242
The MLX90242 is a CMOS Linear Hall Effect sensor IC. It possesses active error
correction circuitry which virtually eliminates the offset errors normally associated
with analog Hall Effect devices.
The ratiometric output voltage is proportional to the supply voltage. When using the
supply voltage as a reference for an A/D converter, fluctuations of +10% in supply
voltage will not affect accuracy.The voltage at the output will increase as a South
magnetic field is applied to the branded face of the MLX90242.
A North magnetic field will cause it to decrease.
In the SOT-23 package the behavior is reversed.
A North field will increase and a South field decrease the output voltage.

Features and Benefits
• Small Plastic Package (SOT-23, TO-92)
• Quad Switched Hall Plate / Chopper Stabilized Amplifier
• Ratiometric Output for A/D Interface
• Low Quiescent Voltage Thermal Drift

SMD Programmable Linear Hall Sensor IC
MLX90292
MLX90292 is a SMD Programmable Linear Hall Sensor IC with digital output dedicated for position sensor
applications with high safety requirements and/or small data latency.
The measured magnetic flux density is conditioned through a fast DSP and reported through a digital
communication channel feat. a 2-wire PAS4, PSI5 or PWM as well as 3-wire PWM mode. Latency time is less
than 500 us.
The MLX90292 is available in TSSOP-16 package feat. 2 independent and isolated dies for redundancy purpose.

• Programmable Hall effect sensor
• > 12-bit magnetic flux density
• > 8-bit temperature (PAS4 & PSI-5)
• > Extensive diagnostic
• > Embedded µ-controller
• > Piecewise linearization
• 2-/3-Wire PWM Mode (up to 2kHz)
• Dual die for redundancy (safety)
• Measurement range from ±30mT to ±170mT
• Programmable through the connector
• Dual customer area for supply chain split
• Over 48 bit customer IDs available
• TSSOP16 SMD package RoHS compliant
• Lead free component, suitable for lead free soldering profile 260°C

Special-Purpose Hall ICs
Differential Dynamic Hall Effect Sensor:

MLX90254
The MLX90254 is a Differential Dynamic Hall Effect Sensor which has been developed
for automotive crankshaft and ABS (anti-lock brake system) applications.
The IC, combined with a magnet placed at his back, offers speed and position sensing
of ferromagnetic tooth-wheels in dynamic operation (non zero speed). Its low
hysteresis enables it to operate over a wide range of airgaps from -40°C to 150°C.
The output structure is an Open-Drain NMOS transistor with a capability of 25 mA
under 24V and protected against short-circuits. The IC is packaged in 4-SIP VA.

• Differential hall sensor
• Low consumption
• Excellent repeatability performance
• Large airgap range
• Large supply voltage range
• Distance between Hall plates : 2.25 mm

Programmable high speed Hall effect
sensor IC
MLX91209
The MLX91209 is a fully customer-programmable monolithic Sensor IC packaged in standard SIP
package.
The Hall Sensor provides a high speed analog output signal proportional to the external applied
flux density. The MLX91209 enables the user to construct a precise current sensor solution with
fast response time of 3µs.

The MLX91209 sensor is automotive qualified and particularly appropriate for DC and/or AC
current measurements up to 200kHz with galvanic isolation, fast response time and small
package size.
The MLX91209 features over voltage and reverse voltage protection including diagnostics. The
transfer characteristic of the MLX91209 is fully customer programmable (offset, sensitivity and
response time).

Current Sensor Applications
In the typical application the sensor is used in combination with a ring shaped soft ferromagnetic
core. The Hall-IC is placed in a small air gap and the current conductor is passed through the inner
part of the ferromagnetic ring. The ferromagnetic ring concentrates and amplifies the magnetic
flux on the Hall-Sensor IC which generates an output voltage proportional to the current. The
Melexis MLX91209 is especially well suited for applications requiring very fast response time such
as inverters. It can be used in many different fields such as electrical or hybrid vehicles, solar
panels, etc.

Product Versions
•
MLX91209BA - programmable magnetic sensitivity: 10 to 150mV/mT
MLX91209CA – programmable magnetic sensitivity: 5 to 150mV/mT

• Programmable high speed current sensor
• Fast response time < 3µs
• Large bandwidth DC–200kHZ
• Fast analog output (12 bits resolution DAC)
• Selectable ratio-metric output
• 48 bit ID number
• Single die SIP (VA) package, RoHS compliant
• Lead free component, suitable for lead free soldering, MSL3

Triaxis: The Sky's The Limit
Triaxis® is Melexis’ trademarked term to describe an innovative
magnetic sensor technology capable of 3 axis magnetic field
measurement from a single sensor.
Triaxis® technology used to measure the position of a magnet very
precisely.
It can be used to measure rotational, linear and 3D displacement as
well as sense current flowing in a wire.
It measures the properties of a magnetic field using the Hall Effect and
innovative, patented, flux concentrators, known as "Integrated
Magnetic Concentrators" or IMC.
Depositing a patented magnetic film to the surface of our IC and
applying a specific mathematical formula to the resulting signals we
can, with the same sensor, measure 3 components (x,y and z) of the
applied magnetic flux density. Conventional Hall sensors (including
devices like our MLX90215 Programmable Linear Hall Sensor) are only
sensitive to flux in 1 axis, through the sensor.

Triaxis Features and Benefits
• Triaxis® Magnetometer (BX, BY, BZ)
• On Chip Signal Processing for Robust Position Sensing
• High Speed Serial Interface
• Enhanced Self-Diagnostics Features
• 5V and 3V3 Application Compatible
• Immune to dirt and dust
• Assembly Misalignment Tolerant
• Inexpensive magnet capability
• Single Die – SO8 Package RoHS Compliant
• Dual Die (Full Redundant) – TSSOP16 Package RoHS
Compliant

Triaxis Programmable Position Sensor IC featuring
SPI
MLX90363 General Description
Universal, maximum flexibility for applications development can be accomplished with the
MLX90363. Designed to be paired with an off-the-shelf microcontroller, the MLX90363 relies on
SPI output communication.
The range of position sensing applications are limitless and constrained only by the imagination
of the designer.
This puts the Bx, By and Bz information directly accessible for processing by the embedded
microcontroller. Data from the on chip temperature sensor and from the internal chip diagnostics
can also be digitally transmitted. Programming happens through the same channel.

• Triaxis™ Magnetometer (BX, BY, BZ)
• On Chip Signal Processing for Robust Position Sensing
• High Speed Serial Interface (SPI compatible – Full Duplex)
• Enhanced Self-Diagnostics Features
• 5V and 3V3 Application Compatible
• 14 bit Output Resolution
• 48 bit ID Number
• Single Die – SO8 Package RoHS Compliant
• Dual Die (Full Redundant) – TSSOP16 Package RoHS Compliant

MLX91206
The MLX91206 opens new opportunities for contactless current sensing in renewable
energy applications, Hybrid Electric Vehicle (HEV) and Electric Vehicle (EV). The device is a
customer programmable monolithic Sensor IC featuring the Triaxis Hall technology. It
enables the user to construct small, economical current sensor solutions with fast response
times. The chip directly monitors the current flowing in an external conductor such as a bus
bar or PCB track.

MLX91206 Features and Benefits
• Programmable high speed current sensor
• Fast response time
• Large bandwidth DC– 90kHZ
• Magnetic concentrator (IMC) provides higher Signal to Noise Ratio
• Over voltage and reverse polarity protection
• Broken track diagnostic
• Fast analog output (12 bits resolution DAC)
• PWM output (12 bits resolution ADC)
• Selectable ratio-metric output
• Thermometer output
• Programmable switch function
• 17 bit ID number
• Single die SOIC8 package RoHS compliant
• Lead free component, suitable for lead free soldering, MSL3

References:
Links:
• https://www.google.co.in/
• http://en.wikipedia.org/
• http://en.wikipedia.org/wiki/Hall_effect_sensor
• http://lcr.uns.edu.ar/electronica/Posgrado/EAMTA/2006/Documents/Analogicos/Smart%20H
E%20Sensors%20over%20Regular%20Processes%20-%20part%201.ppt
• http://sensing.honeywell.com/index.php?ci_id=47847
• http://www.allegromicro.com/Design-Center/Technical-Documents/Hall-Effect-Sensor-IC-
Publications/Integrating-Hall-Eff
• http://www.melexis.com/Products-By-Category/Hall-Effect-Sensor-ICs-
1.aspx

Books:
N.W. Ashcroft and N.D. Mermin "Solid State Physics“
T. Ohgaki et al. "Positive Hall coefficients obtained from contact misplacement on evident n-type ZnO films and
crystals“
Robert Karplus and J. M. Luttinger (1954). "Hall Effect in Ferromagnetics". Phys. Rev. 95: 1154–1160.
N. A. Sinitsyn (2008). "Semiclassical Theories of the Anomalous Hall Effect“

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