Patent ID: 8787070
Filing Date: 2014-07-22
Classification: G11C

Abstract:
1. A reference cell circuit comprising: a first reference cell and a second reference cell each of which includes a variable resistance element which reversibly changes between a low resistance state and a high resistance state according to an application of an electric signal, the low resistance state having a resistance value within a first range, and the high resistance state having a resistance value within a second range which has a lower limit value higher than an upper limit value of the first range; a comparator which compares a resistance value of the first reference cell with a resistance value of the second reference cell; a control circuit; an application circuit which applies an electric signal to a reference cell that is one of the first reference cell and the second reference cell and that is selected by the control circuit, the electric signal being for setting the selected reference cell to a target state which is one of the low resistance state and the high resistance state; and an output circuit which electrically connects, to an output terminal, a reference cell that is one of the first reference cell and the second reference cell and that is selected by the control circuit, wherein the control circuit executes a comparison operation and a write operation one or more times, to make the resistance value of the first reference cell or the resistance value of the second reference cell close to a target resistance value that is a lower limit value or an upper limit value of the target state, the comparison operation causing the comparator to perform the comparison, and the write operation causing the application circuit to apply the electric signal to a reference cell that is one of the first reference cell and the second reference cell and that has a resistance value further from the target resistance value according to each result of the comparison by the comparator, and after the write operation, the control circuit executes an output operation which causes the output circuit to electrically connect, to the output terminal, a reference cell that is one of the first reference cell and the second reference cell and that has a resistance value closer to the target resistance value according to a result of the comparison by the comparator.