Patent ID: 11936396
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Measurement (Instruments)
Classification: CPC H  G | IPC H

Claim 4:
5. The AD converter with self-calibration function according to claim 1,
wherein the summation and conversion unit comprises:
a switching section that connects, to a capacitance holding the unit voltage, the input voltage during conversion and either the reference voltage or a ground voltage at the time of calibration;
a summation section including a positive current source for, during conversion, generating a summed voltage by charging the capacitance with any of multiple currents of different magnitudes after the input voltage is held in the capacitance, and a difference computation portion that connects, to an end of the capacitance opposite the positive current source, a base voltage portion that generates a predetermined base voltage or a resistive portion connected to a ground voltage;
a cross-bar switch that switches between a case where the reference voltage is output to one output end and the summed voltage is output to another output end, and a case where the reference voltage is output to the other output end and the summed voltage is output to the one output end; and
a comparator that outputs a comparison signal when a voltage at a positive input end exceeds a voltage at a negative input end while the one output end being connected with the negative input end and the other output end being connected with the positive input end, and
wherein the calibration control section comprises:
a unit voltage correlation measurement processing portion that, when a summed voltage resulting from summation with a coarse adjustment positive unit voltage exceeds a sum of the reference voltage and the offset voltage of the comparator, performs summation of the summed voltage with a fine adjustment positive unit voltage, the coarse adjustment positive unit voltage being a unit voltage generated with a positive current having a large absolute value, and the fine adjustment positive unit voltage being of a smaller absolute value than the coarse adjustment positive unit voltage.