TMR-Based Current Sensors & Sensors Expo 2019

Interview conducted by Zoe PeterkinNov 5 2019

TDK recently added TMR-based Current Sensors to its portfolio – please can you give us some information on the functionality and design of these sensors?

The first Micronas TMR-based sensor family, CUR 42xy, was developed for current measurements in automotive and industrial applications, and is marketed under the trademark curSENS. The CUR 423x sensors allow for non-intrusive, galvanically isolated contactless current measurements based on closed-loop TMR technology.

The sensors are ISO26262 ASIL-B ready and AEC-Q100 qualified. A very good signal-to-noise ratio and a total error below 1% (full scale) over temperature enable precise current measurements and the smallest module integration since no magnetic-field core concentrator is required.

All of the necessary components for a closed-loop circuit, such as compensation coil, Rshunt, and TMR sensor bridge, are integrated into a small 1 mm thin industry-standard TSSOP16 SMD package. By avoiding the need for a large magnetic-field concentrator core, space and costs can be saved. Digital offset and gain temperature compensation, low-pass filter, and clamping can easily be programmed by using TDK-Micronas’ programming toolchain.

What application areas are covered with this new family of sensors?

The galvanically isolated power and sensing circuits are of particular benefit in high-voltage battery monitoring systems of hybrid and electric vehicles (xEV)

Can you explain what coreless applications are and how your products provide solutions?

Contactless and flux concentrator-based current sensor modules are used today for standard battery monitoring applications. Typically, a Hall sensor and a flux concentrator core are used to measure the magnetic field from the busbar through which  the current is flowing.

A core-based magnetic sensor / TDK Micronas

New high-voltage battery applications in xEV cars require accurate measurement of high currents. Magnetic-field concentrator core size is scaling in parallel with the maximum currents being measured. Modules have to measure currents up to three times larger (up to 1500 A) in next-generation batteries for fully electric cars when compared to the ones in use today.

Developers are now addressing these new requirements, including the enlarged size of concentrator cores and increased cost of manufactured current sensing modules. With the TMR technology in a closed-loop setup, the sensor can be placed very close to the busbar, and the bulky core can be removed. The result is highly accurate current sensing with the TMR sensor and a small current sensing module size without a flux concentrator core. The size of a coreless module is estimated to be at least 30% smaller.  

A coreless TMR sensor alternative / TDK Micronas

At Sensors Expo & Conference 2019, TDK was involved in a symposium on real-world consumer healthcare applications for gas sensing technology advances. Please can you summarize the main points from this symposium?

• TDK is productizing a MEMS-based ultra-low power, miniaturized Carbon dioxide, and Carbon monoxide (CO2 and CO) combo sensor.
   
• We are in a selective engagement phase at this time, with a general announcement targeted for 1Q 2020. Selected customers are being supplied with our evaluation kit.
   
• Our sensor is suitable for a wide range of applications, from consumer to indoor air quality (IAQ) to on-demand HVAC, automotive in-cabin, at-home medical, etc.
   
• In addition, TDK is also working on productizing a multi-gas sensing platform based on MEMS technology, targeted for applications involving VOC sensing. VOCs, or Volatile Organic Compounds, are key gases in air quality, personal wellness, consumer, and other applications.

What other products did you showcase this year?

In addition to the Micronas TMR-based current sensor, TDK showcased TMR angle sensors, direct angle sensors, MEMS gyroscopes, MEMS accelerometers, BioMEMS, temperature sensors, pressure sensors, MEMS microphones, ultrasonic time-of-flight sensors, and MEMS motion sensors.

About Andrew Phillips

Andrew joined TDK-Micronas in 2010 as Automotive Sales manager for North America. Andrew has served in a variety of roles at several major semiconductor companies over the past 30 years. These roles include applications support, market development and sales. Andrew received a BSEE degree from Oakland University.