Patent ID: 8922223
Filing Date: 2014-12-30
Classification: G01R

Abstract:
1. A timer circuit utilizing charging or discharging of a capacitance element, the timer circuit comprising: a capacitance element; a reference potential switching unit in which a first reference potential and a second reference potential that is higher than the first reference potential are input, and that provides an output reference potential to an output reference node by switching the first reference potential and the second reference potential to the output reference node; a first judging power supply voltage that outputs a first judging potential that is higher than a ground potential and is lower than the output reference potential; a first comparison unit that comprises a first input terminal connected to the capacitance element, a second input terminal connected to the reference potential switching unit, and a first output terminal; a second comparison unit that comprises a third input terminal connected to the capacitance element, a fourth input terminal connected to the first judging power supply voltage, and a second output terminal; and a control unit that comprises a first judging terminal connected to the first output terminal, a second judging terminal connected to the second output terminal, and a switching signal output terminal connected to the reference potential switching unit, wherein the first comparison unit outputs a first control signal on the basis of the potentials that are inputted to the first input terminal and the second input terminal, the second comparison unit detects that the potential of the capacitance element is out of a pre-specified range on the basis of the potentials that are inputted to the third input terminal and the fourth input terminal, and outputs a first detection signal indicating that a short circuit state of the capacitance element has been detected, and the control unit outputs a second control signal switching the reference potential between the first reference potential and the second reference potential from the switching signal output terminal, on the basis of the first control signal that is inputted to the first judging terminal.