1. Field of the Invention
This invention relates to an integrated circuit device capable of measuring the magnitude of a current flowing through its internal interconnect.
2. Background Art
It is conventionally desired to measure the magnitude of a current flowing through an interconnect in an integrated circuit device. This is intended to control the output current value in a power IC (integrated circuit). A method for measuring the magnitude of a current is to interpose a resistor in the current path and measure the voltage across this resistor. However, in this method, part of the power supply voltage applied to the integrated circuit device is spent to measure the current. Hence, the measurement has become difficult with the recent decrease of output voltage. By way of example, in a conventional power supply IC, the output voltage was 5 V, and the voltage used for current measurement was 50 mV. However, in a recent power supply IC for personal computers, the output voltage is approximately 1 V, and it is difficult to ensure a current-measuring voltage of 50 mV for an output voltage of 1 V. On the other hand, accurate measurement is impossible if the current-measuring voltage is reduced to approximately e.g. 10 mV in accordance with the output voltage.
Thus, there is a demand for means for measuring the magnitude of a current without intervention in the current path. One such means is a Rogowski coil (see, e.g., JP-A 2006-189319). The Rogowski coil is a ring-shaped coil in which its interconnect is wound around a ring-shaped body, and a returning lead is provided inside the coil. If a target interconnect to be measured is inserted into the ring-shaped body, an induction current is generated in the coil, and the magnitude of a current flowing through the target interconnect can be measured irrespective of the position of the target interconnect with respect to the ring-shaped body and the external magnetic field.
To use such a Rogowski coil to constantly measure the magnitude of a current flowing through the target interconnect, it is desirable to integrate the Rogowski coil and the target interconnect on the same substrate. However, there is a problem in that the Rogowski coil is difficult to integrate because its coil needs to be wound completely around the target interconnect. That is, formation of a Rogowski coil around a target interconnect in an integrated circuit device requires at least seven interconnect layers, including the target interconnect and the returning lead.