“Current control is the key to improving the performance of the motor. How to accurately measure the strength of the current requires an accurate current sensor. The current sensor using TMR technology will be one of the ideal choices for related applications. This article will introduce you the characteristics of TMR technology, the types of current sensors, and the product characteristics of Crocus Technology TMR current sensors sold by Murata, to provide you with a reference when choosing a product.

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Current control is the key to improving the performance of the motor. How to accurately measure the strength of the current requires an accurate current sensor. The current sensor using TMR technology will be one of the ideal choices for related applications. This article will introduce you the characteristics of TMR technology, the types of current sensors, and the product characteristics of Crocus Technology TMR current sensors sold by Murata, to provide you with a reference when choosing a product.

TMR technology enables high magnetic sensitivity and stable performance

TMR (tunneling magnetoresistance) refers to a magnetoresistance effect that occurs in a magnetic tunnel junction (MTJ), which consists of two conductive magnetic layers flanked by a thin (nanoscale) but highly robust insulating layer, One magnetic layer has a fixed orientation of the magnetic moment, while the other layer is free to change to follow the direction of the local magnetic field. When the insulating layer is quite thin, electrons can tunnel from one ferromagnetic body to the other, and the magnitude of the tunneling resistance varies with the relative orientation of the two ferromagnetic materials. The magnetoresistive effect is the scientific basis for magnetic read/write heads in magnetoresistive random access memory (MRAM) and hard disks, and is also used in sensing.

Sensors using TMR technology sometimes serve the same purpose as Hall effect sensors, but work in a completely different way because TMRs are based on different physical phenomena, which explains their superior properties as magnetic sensors, the magnetoresistive effect is the The characteristic of changing its resistance value under the influence of an external magnetic field enables electrical detection of various magnetic fields in various applications.

Crocus Technology has developed and applied its innovative XtremeSense® TMR technology to provide superior magnetic induction performance for many applications. XtremeSense® TMR technology enables high magnetic sensitivity, stable performance over temperature, low noise and low power consumption, making it useful in a variety of end products and markets.

Current sensor detects current for further analysis and control

The current sensor is a device that can detect the current in the wire and generate a signal proportional to the current. The generated signal can be an analog or digital voltage or current signal. These signals can be connected to a meter (such as an ammeter ) Display, and can also be stored in a data capture system for further analysis or control.

The current sensed by the current sensor and the output signal can be analog output or bipolar output when AC input, which can replicate the waveform of the sensed current, or unipolar output, which will be related to the average or RMS value of the detected current. proportional. At DC input, a unipolar output can be used to replicate the waveform of the induced current, or a digital output can be switched when the detected current exceeds a certain threshold.

The measurement of current can be classified according to basic physical principles, such as Faraday’s Law of Induction, Magnetic Field Sensors, Faraday Effect, Hall Effect Sensors, Transformer or Current Clamp Meters, Fluxgate Sensors, Shunt Resistors, Fiber Optic Current Sensors, Rogow Rogowski coil (Rogowski Coil), magnetoresistance (MR), etc. The TMR introduced in this article belongs to the magnetoresistance technology. In addition to TMR, magnetoresistance-based sensors also include anisotropic magnetoresistance (AMR), giant magnetic These magnetic field sensors are suitable for AC and DC current detection, with higher accuracy than the Hall effect, and have been widely used in the industry.

Low-power, high-sensitivity, high-accuracy sensor

Magnetic sensor products from Crocus are based on its innovative XtremeSense® TMR technology, which utilizes monolithic technology to allow magnetic sensors to be fully integrated on a proprietary CMOS lithography process, simplifying manufacturing and enabling a higher level of integration and performance indicators, and can achieve high sensitivity, low noise and stable performance over a wide temperature range.

These magnetic sensors not only have high magnetic sensing performance, but also have the advantages of reliability, small size, galvanic and thermal isolation, high frequency operation and low power consumption, with high sensitivity and low noise and low power consumption at the nanometer scale The range provides high reliability and stable magnetic performance, and also provides excellent robustness in extreme operating environments. These characteristics make it ideal for many different operating environments and applications where accuracy and fast response are important, ideal sensing solutions for IoT and industrial applications, widely used in motor/motion control, energy management systems, inverse inverters, battery management, charge management and many other applications.

The TMR sensors introduced by Crocus include current sensors (contact, non-contact) and position sensors (switch, one-dimensional, two-dimensional). The contact current sensor introduced in this paper is high resolution, high bandwidth and fully integrated Sensors are solutions for products such as solar power systems, battery management systems, server power distribution units (PDUs), motor controls, motors, refrigerators, laptops, and security components.

High Precision Isolated TMR Current Sensor

The CT43x XtremeSense® TMR sensors by Crocus are 1 MHz bandwidth, high precision isolated current sensors with overcurrent fault detection. The CT430 (VCC = 5.0 V) and CT431 (VCC = 3.3 V) are both high bandwidth and Ultra-low noise integrated touch current sensor that uses Crocus Technology’s XtremeSense® TMR technology to provide high accuracy current measurement for many consumer, enterprise and industrial applications. It supports eight current ranges, where the integrated current-carrying conductor (CCC) will handle currents up to 65 A and generate the current measurement as a linear analog output voltage. It achieves a total output error of less than ±1.0% full scale (FS) over voltage and over temperature (-40°C to +125°C).

The CT43x XtremeSense® TMR sensors have a fast response capability of 1 MHz bandwidth and 300ns response time, current consumption is about 6.0 mA, CT430 has a high signal-to-noise ratio (SNR) of 9.0 mARMS, CT431 has an ultra-low noise of 9.5 mARMS, and both have Integrated common mode field rejection of -54 dB to ensure stray fields do not affect measurements in working applications. The CT43x has an integrated overcurrent detection (OCD) circuit that recognizes the out-of-range current output on the fault pin (FLT#), which is an open-drain, active-low digital signal that can be activated by the CT43x to alert e.g. A fault condition that occurs with the microcontroller. Available in an industry standard 16-pin SOIC-Wide package, the CT43x is UL/IEC 62387, UL1577 and IEC 61000-4-5 certified, “green” and RoHS compliant. CT43x can be widely used in motor control, PLC/control boards, solar/power inverters, outdoor products, UPS, SMPS and telecom power supplies, battery management systems, smart appliances, smart meters, residential/commercial HVAC, industrial equipment, Power supply, overcurrent fault protection and other fields.

Epilogue

The current sensor has a wide range of applications and plays a key role in the efficiency of motor operation. The Crocus TMR current sensor introduced in this article has the characteristics of high bandwidth, ultra-low noise and high precision. It will be used in motor control and various consumer and industrial applications. one of the ideal choices.