Patent ID: 8405538
Filing Date: 2013-03-26
Classification: H03M

Abstract:
1. A cyclic A/D converter comprising: an A/D conversion circuit; a residual voltage generation circuit configured to generate a residual voltage by amplifying a differential voltage between an input voltage, which is applied to the A/D conversion circuit, and a predetermined analog voltage; an input circuit configured to select a residual voltage outputted from the residual voltage generation circuit or an input voltage inputted from an external side and apply a selected voltage to both the A/D conversion circuit and the residual voltage generation circuit; a control circuit configured to control the input circuit and the residual voltage generation circuit so that the A/D conversion circuit performs an A/D conversion of the residual voltage outputted by the residual voltage generation circuit while using, as the predetermined analog voltage of the residual voltage generation circuit, a D/A conversion value of a digital conversion value outputted from the A/D conversion circuit to circulate the residual voltage through the input circuit, the A/D conversion circuit and the residual voltage generation circuit; and an input switching circuit configured to switchably input an external signal charge to the residual voltage generation circuit, wherein the control circuit is configured to control the input switching circuit to input the external signal charge to the residual voltage generation circuit, control the residual voltage generation circuit to perform a voltage conversion operation for outputting a converted voltage corresponding to the external signal charge and control the input circuit to select the converted voltage for application to the A/D conversion circuit and the residual voltage generation circuit, before the A/D conversion circuit starts the A/D conversion operation of the converted voltage outputted from the residual voltage generation circuit.