| 摘要 |
PROBLEM TO BE SOLVED: To automatically set a sampling time in accordance with an input impedance value depending on an external device connected purposefully.SOLUTION: An AD conversion circuit includes: a sample and hold circuit 3 for applying an analog input voltage input from an input terminal to a capacitance array 1 of a plurality of capacitances to store an electrical charge for a set sampling time; a comparator circuit 4 for comparing a voltage of each capacitance of the capacitance array sequentially read out from the capacitance with a preset reference voltage, and generating a digital signal; and a sampling time adjustment circuit for measuring a time in which a voltage increasing on the input side of the sample and hold circuit according to an adjustment voltage of the same value as the reference voltage input from an external device connected to the input terminal reaches a threshold predetermined relative to the reference voltage, and setting a time determined on the basis of the measured time as the sampling time. |
