B8.4 - Characterisitics of TMR Angle Sensors

SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
Proceedings SENSOR 2011
B8 - Magnetic Sensors
H. Yamazaki, H. Hirabayashi, N. Oyama, M. Sakai - TDK Corporation, Nagano (Japan)
361 - 365


Magnetic angle sensors are widely used for detecting the rotational angles of motors because of their non-contact operation and the fact that they are not influenced by oil sludge. We have developed and evaluated tunneling magnetoresistive (TMR) angle sensors. In this paper, the characteristics of the TMR angle sensors are described.
TMR is characterized by its very high MR ratio (delta R/R). Consequently, the signal output is much higher than other magnetic sensors such as AMR (anisotropic magnetoresistive) and GMR (giant magnetoresistive). In addition, because of their current perpendicular to plane structure (CPP), TMR angle sensors enable a wider variation in the shape of the magnetic tunnel junction (MTJ) than is possible for GMR and AMR, which utilize the current in-plane structure (CIP). The TMR angle sensor consists of two Wheatstone bridges where the direction of the pinned layer magnetization is mutually orthogonal. TMR is formed by the DC magnetron sputtering method. A shape with small shape-anisotropy was adopted for the MTJ in order that the magnetization direction of the free layer can follow a weak magnetic field. An applied voltage of 5 V was used as test conditions. The offset and amplitude at room temperature were measured, and the angle error was calculated. We have evaluated the TMR angle sensors which generated 3000 mVpp output signals. For the setup that consisted of two orthogonal Wheatstone bridges, the angle error was equal to or less than ±0.1 degrees. In addition, the offset change observed was 1 mV or less (Vcc=5 V). An ESD robustness 8 kV or higher (HBM)was also confirmed.