Patent ID: 9285822
Filing Date: 2016-03-15
CPC Classification: G05F

Claim Text:
1. A reference voltage generating circuit, comprising: a bandgap reference circuit generating a bandgap reference voltage; and a filter circuit for smoothing said bandgap reference voltage, wherein said bandgap reference circuit includes: a reference voltage circuit that is configured to include an operational amplifier receiving a first input voltage at one differential input terminal and receiving a second input voltage at the other differential input terminal, and that generates said bandgap reference voltage based on an output voltage of said operational amplifier; and a switch circuit for alternately switching between the differential input terminal receiving said first input voltage and the differential input terminal receiving said second input voltage, in synchronization with a clock signal, and said filter circuit operates in synchronization with said clock signal and calculates a moving average value of said bandgap reference voltage in a most recent one clock cycle, wherein said reference voltage circuit is configured to generate said bandgap reference voltage having a first voltage value when said clock signal is in a first logic level, and to generate said bandgap reference voltage having a second voltage value different from said first voltage value when said clock signal is in a second logic level, said filter circuit includes: a first capacitive element charged with said bandgap reference voltage having said first voltage value in a first clock cycle; a second capacitive element charged with said bandgap reference voltage having said second voltage value in said first clock cycle; a third capacitive element charged with said bandgap reference voltage having said first voltage value in a second clock cycle immediately before or after said first clock cycle; and a fourth capacitive element charged with said bandgap reference voltage having said second voltage value in said second clock cycle, and in said second clock cycle, said filter circuit outputs said bandgap reference voltage having a magnitude corresponding to an average value of charging voltages of said first and second capacitive elements, and in said first clock cycle, said filter circuit outputs said bandgap reference voltage having a magnitude corresponding to an average value of charging voltages of said third and fourth capacitive elements.