Crocus Whitepaper
What is XtremeSense™ TMR?
As magnetic sensing demand continues to increase, driven by the applications and use
cases that employ them, both in position and current sensing, the demands for
performance and accuracy in sensor technology are rendering legacy solutions like Hall-
effect and Shunt obsolete.
Enter the Tunnel Magneto-Resistance effect (TMR). Unlike legacy solutions, TMR is the
latest magnetic sensor technology and has the inherent advantages of being less
susceptible to temperature change, while offering extremely high magnetic sensitivity.
Other advantages of this new go-to solution include high SNR, low power consumption,
programmable overcurrent detection and fault pin, bidirectional sensing, and high-
voltage isolation to ensure safety.
Highly versatile TMR technology solutions provide high-end performance for demanding
applications and can be incorporated into existing designs with better performance
while lowering overall total solution cost.
Finally, TMR is dramatically simpler than traditional solutions, with its reduced
component count, delivering less reliance on the supply chain.
Within xMR technologies (AMR, GMR, TMR), there is a false assumption that you receive
similar levels of performance, stability , and robustness. In fact, the intrinsic sensitivity
of TMR is high, orders-of-magnitude higher than other XMR technologies.
While many magnetic sensor companies worldwide are featuring TMR-based products
due to their higher level performance benefits, all solutions are not created equal.
Crocus sensors are a premium performance solution, based on XtremeSense® TMR
which provides the highest accuracy, low power, high bandwidth, high sensitivity,
temperature stability, low noise, and the smallest size by comparison to other magnetic
technologies.
What is the resolution of the magnetic sensor ?
Sensor resolution refers to the minimum value of a magnetic field characteristic (field
strength, angular orientation, or equivalent electric current for example) which the
sensor can resolve.
The sensor resolution is determined by evaluating the signal-to-noise ratio (SNR) of the
sensor in its operating conditions. It should not be confused with the analog-to-digital
converter (ADC) resolution of the device or the sensitivity value of the device. For
example, a sensor with 50mV/mT sensitivity does not necessarily have lower noise than
a 5mV/mT sensor.
The intrinsic sensitivity of TMR is high, orders-of-magnitude higher than other xMR
technologies. Consequently, to gain a competitive advantage in SNR, one needs to focus
on reduction of the sensor noise. Years of Research and Development at Crocus
Technology have resulted in TMR sensor designs with the lowest noise on the market.
This low noise technology appears in all XtremeSense based sensors and yields industry-
leading resolution numbers such as:
• 5mA on CT110 Current Sensor, 30kHz Bandwidth
• 10mA on CT430 Current Sensor, 1MHz Bandwidth.
• 0.005degree on CT310 Angle Sensor
The figure below shows a typical open-loop Hall-effect sensor (left in red) and a close-
loop flux-gate current sensor (right in red) along with CT4xx current sensor (in blue).