Patent ID: 7612699
Filing Date: 2009-11-03
Classification: H03M

Abstract:
1. An A/D converter circuit for converting an analog voltage signal input to an input signal line into a binary digital data and outputting the same to an output data line, the A/D converter circuit comprising: a first pulse circulating circuit in which a plurality of inverting circuits is coupled together like a ring, the plurality of inverting circuits using the analog voltage signal input from the input signal line as a power supply voltage, and of which an inverting operation time for inverting and outputting the input signal varying depending upon the power supply voltage, one of the plurality of inverting circuits being configured as a start-up inverting circuit of which the inverting operation can be controlled from an outer side, and the pulse signal circulating in response to a start of operation of the start-up inverting circuit; a first counter for counting the number of times of circulation of the pulse signal circulating in the first pulse circulating circuit and for outputting a counted value; a first latch for holding a counted value output from the first counter as data of last time for a predetermined period and for outputting the same; first operation means which regards the counted value output from the first counter as a present data, subtracts, from the present data, the data of the last time output from the first latch that has stored the data at a time point one period before the time point at which the present data was output, and outputs a subtracted result as a first digital data; inverting means that inverts the analog voltage signal in an increasing/decreasing direction based on nearly an intermediate voltage in a range of the power supply voltage in which the first digital data output from the first operation means varies nearly constantly relative to a change in the power supply voltage, and outputs an inverted analog voltage signal; a second pulse circulating circuit in which inverting circuits that use the inverted analog voltage signal as a power supply voltage signal and of which the inverting operation time for outputting an input signal in an inverted manner varies depending upon the power supply voltage, are connected in the same number and in the same manner as the inverting circuits that constitute the first pulse circulating circuit, one of the plurality of inverting circuits being configured as a start-up inverting circuit of which the inverting operation can be controlled from the outer side, and the pulse signal circulating in response to a start of operation of the start-up inverting circuit; a second counter for counting the number of times of circulation of the pulse signal circulating in the second pulse circulating circuit and for outputting a counted value; a second latch for holding a counted value output from the second counter as inverted data of last time for a predetermined period and for outputting the same; second operation means which regards the counted value output from the second counter as a present inverted data, subtracts, from the present inverted data, the inverted data of the last time output from the second latch that has stored the data at a time point one period before the time point at which the present inverted data was output, and outputs a subtracted result as a second digital data; and third operation means for subtracting the second digital data from the first digital data and for outputting a subtracted result to the output data line as the binary digital data.