Automotive, CASE Trend Transforms into Sensor Aggregation
Magnetic sensor, can measure object displacement without contact
Infineon 3D Hall Sensor with Multiple Low-Power Features


Magnetism is a phenomenon in which substances attract or repel each other due to electric charges. Although we cannot see them, we can easily encounter magnets around us, and their strength can be measured without difficulty. The Earth itself is already a giant magnet.

As the use of automation, remote control, and predictive maintenance in various industries including automobiles increases significantly, the use of sensors that measure the movement and location of objects is becoming more prominent. At the same time, the adoption of magnetic sensors is also increasing.

Magnetic sensors are useful for measuring the position and movement of objects, and among them, three-dimensional (3D) Hall sensors are optimal for detecting complex movements and have fewer installation location restrictions, so they can be said to be highly utilized.

We met with Park Ju-il, managing director in charge of automotive sensor semiconductors at Infineon Technologies Korea, and asked him about the characteristics and usability of magnetic sensors, as well as their future prospects.


Q. The percentage of semiconductors installed in automobiles is increasing. In particular, many sensors are being installed for driver safety and convenience. What are the recent trends in the automotive sensor market?
A. Recently, automobiles are changing into automobiles with a different concept from the existing ones. The wave of changes in automobile technology can be largely divided into four: Connectivity, Autonomous Driving, Sharing/Subscription, and Electrified Powertrain, which are commonly abbreviated as 'CASE'.

New trends are demanding new requirements and functions in the automotive parts market. To meet these requirements, a variety of sensors must be used in large quantities, so the importance of sensors and the market size are increasing day by day.

In the autonomous driving field, the adoption rate of radar, lidar, and camera sensors is increasing to implement level 3 autonomous driving functions. In addition, MEMS sound detection sensors, which were not previously required, are also being newly adopted to detect external sounds of the car. In the future, cars will become a moving sensor collection.

Some sensors are actually losing ground in the market due to the four waves of change. MAP, crank angle, and cam angle sensors used in internal combustion engines are expected to lose ground as electric vehicles expand in line with strengthened environmental regulations.

As the electric vehicle market expands, magnetic sensors will be utilized as rotor position and current sensors in motors, etc., and pressure sensors are expected to be transferred to applications such as battery monitoring. In addition, the hydrogen sensor market is expected to grow along with the growth of the hydrogen car market.


Q. There are various types of sensors. What is the principle of magnetic sensors that detect magnetic fields, and in what applications are they mainly used?
A. Currently commercialized magnetic sensors are divided into those that use the Hall effect and those that use the magnetoresistive (MR) effect. The MR method is also divided into AMR, GMR, and TMR methods depending on the implementation principle.

The reason why all of these methods coexist so far is because there are advantages and disadvantages depending on the magnetic sensor measurement principle. In the case of the MR method, it is advantageous in realizing high sensitivity, but there is a limitation in the magnetic measurement range. However, the Hall effect method is relatively free in the magnetic measurement range.

Humans have been using magnetic sensors in various fields since the compass a long time ago. The demand for magnetic sensors is expected to continue to increase. This is because magnetic fields are physical quantities that we can easily encounter around us. In addition, they can measure mechanical displacement without contact, so they are highly durable and reliable, and are used in a wide range of industries, including automobiles.


Q. What type of sensor uses the Hall effect among magnetic sensors, and what is the difference between a 3D Hall sensor and a Hall sensor?
A. Hall sensors are used in Hall switch sensors that determine whether a magnet is approaching, and linear Hall sensors that continuously measure an externally applied magnetic field.

The magnetic field we encounter in the real world is a three-dimensional vector. That is, the magnetic field vector component can be decomposed into x-axis, y-axis, and z-axis components based on the rectangular coordinate system. Existing linear Hall sensors can only measure the magnetic field component perpendicular to the Hall plate surface. Therefore, it is called a one-dimensional (1D) magnetic sensor.

A 3D Hall sensor is a sensor that implements three 1D linear Hall sensors into one, with one 1D linear Hall sensor positioned in each of the x, y, and z directions. Therefore, a 3D Hall sensor can measure the three-dimensional vector of an applied magnetic field.


Q. Why do you think 3D Hall sensors will be useful in various applications?
A. Magnetic sensors are used to measure the displacement of objects without contact. However, the displacement of objects varies depending on the application. It can perform linear motion, rotational motion, and combined linear and rotational motion, and the more complex and compound the motion, the higher the degree of freedom.

3D Hall sensors are suitable for measuring displacement of high-degree-of-freedom movements. This is because a lot of information is needed to determine the displacement of high-degree-of-freedom movements. The maximum information that the magnetic field can provide due to the displacement of the magnet at a specific point is the three-dimensional magnetic vector. 3D Hall sensors can obtain all of this three-dimensional magnetic information.

1D Hall sensors can measure the linear displacement of a magnet by displacing the magnet in a direction perpendicular to the 1D linear Hall plate. However, it is difficult to measure the motion of a magnet with two-dimensional displacement (x, y). This is because multiple positions are mapped to a single measured magnetic quantity, and there is no 1:1 correspondence between the measured magnetic quantity and the displacement.

3D Hall sensors can map a measured three-dimensional magnetic field to various positions 1:1. This means that by measuring the magnetic field caused by the displacement of the magnet, the displacement of the position vector can be calculated in reverse. This is because, mathematically, for a 1:1 correspondence function, an inverse function always exists.

The 3D Hall sensor, a composite of 1D and 2D magnetic sensors, can easily measure movements with a higher degree of freedom than the two sensors, and has a high degree of freedom in selecting sensor positions, making it suitable for applications with many constraints in mechanical design.

Furthermore, since it is possible to obtain all three-dimensional magnetic field vector information applied to the sensor, it has the advantage of being able to perform additional functions and services such as fault diagnosis when an abnormal magnetic field vector is measured simultaneously with position measurement.


Q. What are the strengths of Infineon’s 3D Hall sensor product line compared to other products?
A. Infineon's 3D Hall sensor family supports a wide range of applications from consumer to automotive. It also supports a wafer level package (WLP) designed for mobile applications.

As a functional feature, it supports ultra-low power. It consumes only 7nA of current in standby mode, and only consumes about 3.4mA for less than 1ms when measuring a magnetic field, so it is possible to implement low power. For example, when performing continuous measurements every 100Hz, the average current consumption is several tens of uA.

It also supports wake-up function for low-power implementation at the system level. Infineon's 3D Hall sensor measures magnetic field by itself at set intervals when the host system is in low-power mode or standby mode, and when a movement event is detected, it notifies the host system of the event as an interrupt.

It also supports various measurement modes for application operation convenience. For example, the sensor itself can measure the magnetic field at a specific interval and, when the measurement is complete, send a measurement completion signal to the host MCU as an interrupt. In addition, the host MCU can request the sensor to measure the magnetic field whenever necessary.

Additionally, since it supports I2C communication, up to four sensors can be connected to a single bus. This means that up to four sensors can be used simultaneously without expanding the MCU port.

It has its own built-in temperature sensor, allowing applications to implement temperature compensation of the magnetic field according to changes in the ambient temperature. It also provides self-fault diagnosis information for high-reliability automotive applications.

3D Hall sensors measure various types of motion displacement, but if the magnetic field vector information is processed with calculations already specified in the DSP built into the sensor, the degree of freedom of the application decreases, and the price increases due to the additional DSP built in.

On the other hand, Infineon's 3D Hall sensor has a simple internal structure and the MCU handles additional operations, so it offers high design and application freedom, low price, and high reliability.


Q. What environment or capabilities do you think customers need to have to develop applications equipped with magnetic sensors more quickly?
A. In order to measure the displacement of an object using a magnetic sensor, the most optimized magnetic circuit design is essential. The magnetic circuit refers to designing the relationship between the displacement of the object to be measured and the magnetic field to be measured. The design of such a magnetic circuit is a core competency of magnetic sensor applications.

This is because the competitiveness and differentiation of many position sensors depend largely on the selection of magnetic circuits optimized for the application and the algorithms that process magnetic information. The selection of the optimal magnetic circuit significantly affects the cost structure, performance, and reliability at the system level.

This area is where the core ideas of application developers shine rather than the semiconductor development area. After selecting the magnetic circuit, sensor, and algorithm, the appropriate hardware and software design follows.

Therefore, as an additional capability to support the design of magnetic circuits, the ability to utilize simulation tools to calculate magnetic fields is necessary. If we reuse existing, widely used magnetic circuits and algorithms, wouldn't the simulation tools be unnecessary? Generally, no.

Even if the existing magnetic circuit concept is used, optimization is required according to the constraints of the application, so the use of magnetic circuit simulation is important in many ways in the development of magnetic sensor applications. Furthermore, since the 3D Hall sensor has a high degree of freedom in the design of the magnetic circuit, the importance and weight of simulation are higher than those of other magnetic sensors when measuring complex movements.


Q. What are Infineon’s goals and plans in the future magnetic sensor market?
A. Infineon aims to provide P2S (Product to System)-based services from the customer's perspective and also from the application's perspective including magnetic sensors.

Infineon shares ideas for utilizing magnetic sensors with customers and immediately accepts feedback from customers and the market. Furthermore, based on this collaboration, Infineon strives to become a semiconductor supplier leading magnetic sensor technology.