A/D converter having a dynamic encoder
AssigneeNEC Corporation
InventorSachio Nakaigawa
Life of this patent
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Abstract
An A/D converter includes a resistor ladder for generating a plurality of reference potentials, a comparing section for comparing each of the reference potentials against an input analog signal to output a thermometric code, and a dynamic encoder composed of a combinational circuit to encode the thermometric code to a binary code by responding a clock signal. The A/D conversion is finished in a single clock cycle at a high speed, with a reduced number of elements and reduced power dissipation.
Claims17
An analog-to-digital (A/D) converter comprising:
- a reference voltage generator for generating a plurality of reference voltages;
- a comparing section including a plurality of comparing elements each comparing an input analog signal against a corresponding one of said reference voltages to output a thermometric code;
- and
- a dynamic encoder including a plurality of bit lines and a dynamic combinational circuit transferring said thermometric code to said bit lines by responding to a clock,
- wherein said input analog signal is converted in a single clock cycle to a binary code generated on said bit lines and corresponding to a magnitude of said input analog signal;
- wherein a rate of conversion is substantially independent of a number of bits to be output,
- wherein each comparing element of said comparing section comprises a comparator and a level converter for amplifying an output from said comparator by responding to a clock signal, and,
- wherein said level converter comprises CMOS transistors.
An analog-to-digital (A/D) converter comprising:
- a reference voltage generator for generating a plurality of reference voltages;
- a comparing section including a plurality of comparing elements each comparing an input analog signal against a corresponding one of said reference voltages to output a thermometric code;
- and
- a dynamic encoder including a plurality of bit lines and a dynamic combinational circuit transferring said thermometric code to said bit lines by responding to a clock,
- wherein said thermometric code is converted in a single clock cycle to a binary code generated on said bit lines and corresponding to a magnitude of said input analog signal, and
- wherein said conversion is expressed by the Boolean algebra equation:
- b m = ∑ i = 1 2 ( m - 1 ) ( C ( t x ) × t y )
- wherein N is a number of bits of said binary code, bm is a m-th bit of said binary code counted from most significant bit (MSB), tx is the x-th bit of said thermometric code counted from MSB, ty is the y-th bit of said thermometric code counted from MSB, C(tx) is a complement of tx, 0≦x≦N−2, 1≦y≦2N−1, x=2(i−1)×2(N−m),y={2(i−1)+1}×2(N−m), and 1≦m≦N.
A method for converting a thermometric code to a binary code, comprising:
- transferring a thermometric code to a plurality of bit lines by responding to a clock signal, wherein said conversion is expressed by the Boolean algebra equation:
- b m = ∑ i = 1 2 ( m - 1 ) ( C ( t x ) × t y )
- wherein N is a number of bits of said binary code, bm, is a m-th bit of said binary code counted from most significant bit (MSB), tx is the x-th bit of said thermometric code counted from MSB, ty is the y-th bit of said thermometric code counted from MSB, C(tx) is a complement of tx, 0≦x≦2N−2, 1≦y≦2N−1, x=2(i−1)×2(N−m), y={2(i−1)+1}×2(N−m), and 1≦m≦N.
Dependencies are inferred from the claim text.