| 摘要 |
An A/D converter of a serial-parallel comparison type has both multiplying functions of an analog input data and a digital input data. The analog input data VX is converted into a digital code Ic corresponding to two more significant digits, by a first parallel comparing portion and a first determining circuit, and converted into a digital code If corresponding to two less significant digits by a second parallel comparing portion and a second determining circuit. The digital codes Ic and If are alternately applied to a control circuit by a first selector circuit. Two more significant bits Rc and two less significant bits Rf of a 4-bit digital input data are respectively applied to a control signal generating circuit by a second selector circuit. Multiplications of RcIc, RfIc, RcIf and RfIf are serially performed within the time period of one conversion by the control signal generating circuit and the control circuit. The multiplied results are shifted four bits, two bits, two bits and 0 bits, respectively, and then, added to each other. As a result, the product of the analogue input data and the digital input data is calculated.
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