Appeal No. 1997-3956
Application 08/583,960
upper comparison voltage generating means for dividing a
reference voltage into a plurality of large-level regions with
first voltage-dividing elements and outputting voltages at
boundaries of the individual large-level regions as upper
comparison voltages;
a plurality of upper comparators comparing an analog
input voltage with said upper comparison voltages;
upper determining means for determining, from output
signals of said upper comparators, to which one of said large-
level regions said analog input voltage belongs, wherein said
determining means includes first converting means for
outputting a predetermined upper digital code in accordance
with said determined large-level region;
middle comparison voltage generating means for dividing
said large-level region to which the analog input voltage is
determined to belong by said upper determining means, into a
plurality of middle-level regions with second voltage-dividing
elements and outputting voltages at boundaries of said middle-
level regions as middle comparison voltages, the second
voltage-dividing elements being commonly used with the first
voltage-dividing elements;
a plurality of middle comparators comparing said analog
input voltage with said middle comparison voltages;
middle determining means for determining, from output
signals of said middle comparators, to which one of said
middle-level regions said analog input voltage belongs,
wherein said determining means includes second converting
means for outputting a predetermined middle digital code
corresponding to said determined middle-level region;
lower comparison voltage generating means for dividing
said middle-level region to which the analog input voltage is
determined to belong by said middle determining means, into a
plurality of small-level regions with third voltage-dividing
-3-
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