Currentier

Issue & Solution

For the reasons outlined in that article, Asahi Kasei Microdevices (AKM) developed the unique coreless current sensor IC, titled “Currentier”. Currentier is the outcome of long experience and unique technology AKM has with compound semiconductor magnetic sensors (Hall elements), package design, and analog circuit design. 

Currentier is used in industrial and residential equipment around the world and contributes to meeting the following requirements:

Benefit

  • Reducing system size (i.e. equipment size)
  • Reducing design man-hours
  • Creating a safer system
  • Improving system efficiency and providing more precise control

Unique Core Technology

In part 5, it will be explained here compound semiconductor magnetic sensors (Hall elements) technology, IC design technology, and package design technology applied to Currentier.

Currentier is configured as shown in Figure 1.

  • Magnetic sensor that detects the magnetic field created by the measured current flowing through the primary conductor
  • IC that corrects and amplifies signals from magnetic sensors
  • Package that integrates primary conductor, magnetic sensor, and IC

AKM has its own technology that no other company has in the above three points.

Figure 1. Currentier schematic diagram

AKM has a history of about 50 years as a manufacturer of magnetic sensors, with Hall elements gaining the world's top market share. Currently, AKM Hall elements are used in many applications, including DC brushless motors, cameras, smartphones, and white goods. Despite many magnetic sensor manufacturers around the world, AKM has gained the top share in the world due to its excellent compound semiconductor design and production technology. As shown in "Types and Principles of Hall Elements", the sensitivity of a Hall element is proportional to the parameter called "electron mobility" of the semiconductor material that composes the Hall element.

AKM has world-class design and production technology for III-V compound semiconductors such as GaAs, InAs, and InSb. III-V compound semiconductors feature higher electron mobility than the silicon (Si) used by many competitors.

For example, InAs is known to have more than 20 times the electron mobility of silicon. This means that AKM's InAs Hall elements can achieve a sensitivity 20 times higher than Si Hall elements of other companies. However, a trade-off with this high sensitivity was the deterioration of the temperature characteristics specific to materials with a narrow bandgap (Figure 2).

Figure 2. Characteristics comparison table of semiconductor materials

Combining AKM's long experience in temperature characteristics fluctuations of compound semiconductors and analog IC design technology can improve this deterioration. Currentier has achieved excellent temperature characteristics that are equal to or superior to those of current sensors using Si Hall elements (Figure 3).

Since the sensitivity of the Hall element itself is high, the signal amplification rate inside a IC can be reduced, and a wide bandwidth can be secured. Currentier achieves faster response speed than current sensors using Si Hall elements (Figure 4).

Figure 3. Temperature characteristics comparison table of Currentier CZ37xx and Si Hall element current sensors (competitive products)
Figure 4. Response characteristics comparison table of Currentier CZ37xx and Si Hall element current sensors (competitive products)

In high-speed current control applications, dV/dt and dI/dt dynamic noise characteristics are another important characteristic in addition to response characteristics. If noise due to the parasitic capacitance or parasitic inductance component occurs in response to a rapid change in voltage or current, it will be impossible to obtain a signal at high-speed and accurately even if the bandwidth of the IC itself is wide.

With the packaging and IC design technology accumulated by AKM for many years, Currentier achieves dramatically lower dynamic noise levels than competitors by minimizing the parasitic capacitance and parasitic inductance components inside the device. (Figure 5). As a result, high-speed and accurate current detection is possible even for rapidly changing voltage and current waveforms, and Currentier is being used in various applications that require high-speed response, such as overcurrent detection and DC-DC converters.

Figure 5. Dynamic noise characteristics comparison table of Currentier CZ37xx and Si Hall element current sensors (competitive products)

Lastly, AKM manufactures Currentier products at its own factory, including the assembly process, ensuring stable quality and delivery. Currentier is ideal for applications that require long-term use, such as industrial equipment.

'Currentier' series are open-type current sensor ICs which have the world's smallest package, high accuracy, high S/N ratio, and the world's fastest response time.
With these advantages, we will offer the best current sensing solution to wide-ranging applications, such as inverter control, overcurrent detection, and electrical power detection.

* Currentier is a trademark of Asahi Kasei Microdevices Corporation.