| 摘要 |
PURPOSE:To improve the accuracy of A/D conversion without increasing the number of comparators by storing an electric charge corresponding to the 1st A/D conversion output to a weight capacitor, changing the level and applying the 2nd A/D conversion. CONSTITUTION:A high voltage VR of a reference power VG is fed to one terminal of a resistor group RL at first and an electric charge corresponding to an input signal Vin is stored in an input signal storage capacitor Ci by the conduction of a sampling switch SW1. The A/D conversion is applied based on the signal Vin through comparators COMP1-COMP15 and an encoder ENC and the 1st high-order 4-bit output is fetched in a latch circuit LTC1. The electric charge corresponding to the output is stored in weighting capacitors C1-C4. Then the electric charge is drawn out of a capacitor Ci, the voltage VR is changed over into a VR/16 to apply the 2nd time A/D conversion and the encoder output is fetched in a latch circuit LTC2 as the low-order 4-bit. Thus, the conversion of the signal Vin into an 8-bit digital signal is obtained.
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