Abstract: To provide a compact, high density, highly reliable and low cost three-terminal IC sensor unit, a host device to be connected to the sensor unit, a sensor system comprising such sensor unit and host device and a communication method between sensor unit and host device. The power supply voltage to be supplied to the sensor unit 100 from the host device (external device) 200 through the power supply terminal 101 is turned on/off by power supply on/off means 220 in response to command and/or data to be transmitted and such on/off pulsation of the power supply voltage is detected by the data detection section 140 for transmission from the host device 200 to the sensor unit 100. Also, the current source 160 in the sensor unit 100 varies the load current of the power supply in the host device 200 through the power supply terminal 101 in response to the data and the change in the load current is detected by the current detection section 230 for data transmission from the sensor unit 100 to the host device 200.

Abstract: A current sensor that can reduce a measurement error due to isotropic elongation or strain owing to temperature and the like. A first half bridge circuit is placed in a first region divided by a center line of a mounting substrate, and a second half bridge circuit is placed in a second region, and the half bridge circuits are equally formed and placed point symmetrically about the central point of the mounting substrate. Even if elongation or strain occurs isotropically in the mounting substrate of magnetoresistive elements owing to temperature, the half bridge circuits undergo the influence of the elongation or strain equally as the bridge circuit. Thus, it can cancel the effect and reduce the measurement error due to the isotropic elongation or strain owing to temperature.

Abstract: A current sensor that can reduce a measurement error due to isotropic elongation or strain owing to temperature and the like. A first half bridge circuit is placed in a first region divided by a center line of a mounting substrate, and a second half bridge circuit is placed in a second region, and the half bridge circuits are equally formed and placed point symmetrically about the central point of the mounting substrate. Even if elongation or strain occurs isotropically in the mounting substrate of magnetoresistive elements owing to temperature, the half bridge circuits undergo the influence of the elongation or strain equally as the bridge circuit. Thus, it can cancel the effect and reduce the measurement error due to the isotropic elongation or strain owing to temperature.