Patent ID: 8816683
Filing Date: 2014-08-26
Classification: G01R

Abstract:
1. A magnetic field sensing method using tunneling magneto-resistor (TMR) sensors, comprising: using a first TMR sensor and a second TMR sensor for sensing magnetic field; wherein the first TMR sensor and the second TMR sensor respectively comprise a first magnetic tunneling junction (MTJ) device and a second MTJ device, the first MTJ device and the second MTJ device having a pinned layer, a tunneling layer and a free layer, the pinned layers of the first and second MTJ device having a pinned magnetization at a first pinned direction and the first pinned direction having a first angle Φ to an easy-axis; providing a bias signal to the first and second TMR sensor; in a first period, performing a first sensing operation, comprising: setting a first free magnetization of the free layer of the first MTJ device to be parallel to the easy-axis and to have the first angle Φ to the first pinned direction, setting a second free magnetization of the free layer of the second MTJ device to have a second angle π-Φ to the first pinned direction, and pinning the first free magnetization; and performing magnetic field sensing to obtain a first difference corresponding to conductance difference between the second TMR sensor and the first TMR sensor; in a second period, performing a second sensing operation, comprising: setting the first free magnetization of the free layer of the first MTJ device to be parallel to the easy-axis and to have the second angle π-Φ to the first pinned direction, setting the second free magnetization of the free layer of the second MTJ device to have the first angle Φ to the first pinned direction, and pinning the first free magnetization; and performing magnetic field sensing to obtain a second difference corresponding to conductance difference between the second TMR sensor and the first TMR sensor; in a third period, performing a third sensing operation, comprising: setting the second free magnetization of the free layer of the second MTJ device to be parallel to the easy-axis and to have the first angle Φ to the first pinned direction, setting the first free magnetization of the free layer of the second MTJ device to have the second angle π-Φ to the first pinned direction, and pinning the second free magnetization; and performing magnetic field sensing to obtain a third difference corresponding to conductance difference between the first TMR sensor and the second TMR sensor; in a fourth period, performing a fourth sensing operation, comprising: setting the second free magnetization of the free layer of the second MTJ device to be parallel to the easy-axis and to have the second angle π-Φ to the first pinned direction, setting the first free magnetization of the free layer of the first MTJ device to have the first angle Φ to the first pinned direction, and pinning the second free magnetization; and performing magnetic field sensing to obtain a fourth difference corresponding to conductance difference between the first TMR sensor and the second TMR sensor; summing the first to fourth differences to obtain a sensing value corresponding to magnetic field intensity.