Patent ID: 8314723
Filing Date: 2012-11-20
Classification: H03M

Abstract:
1. A ghost key detecting circuit, comprising: a plurality of switch elements each having a predetermined resistance; at least a set of scan lines; at least a set of return lines, wherein the set of scan lines and the set of return lines are crossed to each other and coupled to the plurality of switch elements, respectively; and a level detecting circuit, coupled to the set of return lines, for performing level detection upon measured voltage values at the set of return lines by comparing the measured voltage values with a reference voltage value to indicate that at least one switch element corresponding to the set of return lines at the set of scan lines is turned on or turned off; wherein, the level detecting circuit further comprises: a first transistor, having a first node coupled to a supply voltage, a second node coupled to a ground level and a control node coupled to a return line for receiving a measured voltage value at the return line, wherein the reference voltage value is a threshold voltage of the first transistor and the first transistor is turned on or turned off based on the measured voltage value; and a second transistor, having a first node for generating a logic signal, a second node coupled to the ground level and a control node coupled to the first node of the first transistor.