US 5,400,029 AGranted

Analog-digital conversion circuit device and analog-digital conversion method

AssigneeSeiko Instruments Inc.

InventorKenichi Kobayashi

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Abstract

A compact and fast analog-digital conversion circuit device is described. A coarse analog digital conversion is carried out by a first voltage-dividing circuit 4 and a first voltage comparing circuit block 5. Thereafter, a particular voltage level specified by the coarse conversion is subtracted from an input analog signal Vin held in a sample and hold circuit 2. A result thereof is processed by a second voltage comparing circuit block 10 to effect a fine analog-digital conversion. By such a construction, a number of analog switches contained in a multiplex circuit block 6 can be reduced significantly. Further, compensative reference voltage levels are formed from a second voltage-dividing circuit 9 by an addition/subtraction circuit 11, and a third voltage comparing circuit block 12 is utilized to compare with an output of a subtraction circuit 7 to thereby compensate for error induced between the coarse and fine conversion.

Claims4

Dependent claims

An analog-digital conversion circuit device comprising:

a sample and hold circuit for sampling an input analog signal and for holding the same for a given period;
a first voltage-dividing circuit for dividing a first base voltage into a plurality of coarse reference voltage levels;
a first voltage comparing circuit block including a plurality of voltage comparing circuits for comparing an output from the sample and hold circuit with the respective coarse reference voltage levels so as to coarsely digitize the input analog signal;
an analog multiplex circuit block for selecting one of the coarse reference voltage levels according to an output of the first voltage comparing circuit block;
a subtraction circuit for subtracting an output of the analog multiplex circuit block from the output of the sample and hold circuit;
a second voltage-dividing circuit for dividing a second base voltage into a plurality of fine reference voltage levels;
a second voltage comparing circuit block including a plurality of voltage comparing circuits for comparing an output of the subtraction circuit with the respective fine reference voltage levels so as to finely digitize the input analog signal;
an addition/subtraction circuit for adding or subtracting the fine reference voltage levels with one another to produce fine compensative reference voltage levels;
a third voltage comparing circuit block including a plurality of voltage comparing circuits for comparing the output of the subtraction circuit with respective outputs of the addition/subtraction circuit;
and
a logic circuit operative based on those outputs of the first, second and third voltage comparing circuit blocks for generating an output digital signal corresponding to the input analog signal.

8 more elements

Dependencies are inferred from the claim text.