AD converter
AssigneesHitachi, Ltd., Hitachi VLSI Engineering Corp.
InventorsTatsuji Matsuura, Imaizumi Eiki, Kunihiko Usui, Takanobu Anbo
Life of this patent
Estimating the term…
Abstract
A high speed, accurate AD converter operable at low supply voltage, even with low gain amplifiers, particularly for a serial-parallel or pipelined AD converter, has a sub AD converter in each block of the second and subsequent stages provided with an adjuster for adjusting the full scale reference voltage in accordance with the gain of the error amplifier of the preceding stage. Analog switches are rendered immune to low operating voltage by being supplied separate voltage higher than the supply voltage of the other components in their circuit.
Claims21
An AD converter in the form of a serial-parallel or pipelined AD converter for low-voltage application to convert a beginning analog signal to a final digital signal, comprising:
- a plurality of function blocks, each operating as a stage of AD conversion;
- each of said blocks comprising a sub AD converter having a reference voltage, an analog signal input and a digital output;
- each of said blocks further comprising a DA converter inputting the digital output and outputting an analog signal output, and an error amplifier comparing the analog signal input and the analog signal output to produce an amplified analog differential residue signal;
- said blocks being connected as means for AD conversion of the beginning analog signal input to said sub AD converter of a first stage of the stages of AD conversion for providing the digital output of each of said blocks as at least one bit of the final digital signal, and providing the amplified analog differential residue signal of each of said blocks having a next block of the stage of AD conversion as the analog signal input of the next block;
- said sub AD converter in each block at a second and following ones of the stages of AD conversion having a voltage divider, a full scale adjusting amplifier means for generating and adjusting a reference voltage to be substantially equal in full scale to a full output range of said error amplifier of a preceding stage of AD conversion and for supplying the reference voltage across said voltage divider;
- and
- said full scale adjusting amplifier means having an amplifier that is identical in circuit construction type to said error amplifier and inputs one voltage step of the voltage divider in the block at a preceding one of the stages of AD conversion.
An AD converter in the form of a serial-parallel or pipelined AD converter, which is contained on an single integrated circuit, for low-voltage application to convert a beginning analog signal to a conversion digital output, comprising:
- a plurality of function blocks, each operating as a stage of conversion;
- each of said blocks comprising a sub AD converter having a reference voltage, a voltage divider providing the reference voltage, an analog signal input and a digital output;
- each of said blocks further comprising a DA converter inputting the digital output of said sub AD converter and outputting an analog signal output, and an error amplifier comparing the analog signal input to the analog signal output to produce an amplified analog differential residue signal;
- said blocks each being means for AD conversion of the beginning analog signal as the analog signal input at a first of the stages of AD conversion, for providing at least one bit of the conversion digital output as the digital output, and for AD conversion of the amplified analog differential residue signal fed from a preceding one of the stages of AD conversion as the analog signal input at the stages other than the first of the stages of AD conversion;
- and
- said error amplifiers each being a switched capacitor amplifier having analog MOS switches with a gate control voltage higher than power supply voltage of the integrated circuit.
An AD converter in the form of a serial-parallel or pipelined AD converter for low-voltage application to convert a beginning analog signal to a final digital signal, comprising:
- a plurality of function blocks, each operating as a stage of AD conversion;
- each of said blocks comprising a sub AD converter having a reference voltage, an analog signal input and a digital output;
- each of said blocks further comprising a DA converter inputting the digital output and outputting an analog signal output, and an error amplifier comparing the analog signal input and the analog signal output to produce an amplified analog differential residue signal;
- said blocks being connected as means for AD conversion of the beginning analog signal input to said sub AD converter of a first stage of the stages of AD conversion for providing the digital output of each of said blocks as at least one bit of the final digital signal, and providing the amplified analog differential residue signal of each of said blocks having a next block of the stage of AD conversion as the analog signal input of the next block;
- said sub AD converter in each block at a second and following ones of the stages of AD conversion having a voltage divider, a full scale adjusting amplifier means for generating and adjusting a reference voltage to be substantially equal in full scale to a full output range of said error amplifier of a preceding stage of AD conversion and for supplying the reference voltage across said voltage divider;
- and
- said full scale adjusting amplifier means having an amplifier that operates within the same circuit characteristics as said error amplifier and inputs one voltage step of the voltage divider in the block at a preceding one of the stages of AD conversion.
Dependencies are inferred from the claim text.