Pipeline A/D converter and digital camera
View Patent ↗In each of a plurality of stages, an input analog signal is quantized, so that a digital signal corresponding to each part of bits is generated. ADA conversion portion generates an analog reference signal based on the digital signal, and a remainder operation portion performs addition/subtraction and amplification by a predetermined factor with respect to the input analog signal. Then, the signal thus obtained is supplied to a subsequent stage. The DA conversion portion in the first stage where A/D conversion of a plurality of bits is performed includes primary voltage supply portions capable of outputting a reference voltage at one of a plurality of levels, and an auxiliary voltage supply portion capable of outputting a reference voltage at an auxiliary level different from the above-described level. The respective voltage supply portions selectively output the reference voltages based on a digital signal generated by an AD conversion portion. Based on a combination of the output reference voltages, the analog reference signal in accordance with the digital signal is generated. It is possible to reduce power consumption while suppressing an increase in the area of an element.
1. A pipeline A/D converter having a plurality of stages connected in cascade, each performing A/D conversion for each part of bits, so as to convert an analog signal input to a first stage into a digital signal sequentially in descending order of bit significance through the plurality of stages,
each of the stages comprising:
an AD conversion portion that quantizes the input analog signal of a current stage so as to generate the digital signal corresponding to the part of bits;
a DA conversion portion that generates an analog reference signal based on the digital signal output from the AD conversion portion; and
a remainder operation portion that adds/subtracts the analog reference signal to/from the input analog signal of the current stage and amplifies the obtained analog signal by a predetermined factor so as to generate a remainder analog signal, and supplies the reminder analog signal to a subsequent stage as the input analog signal,
wherein the first stage among the plurality of stages is configured to perform A/D conversion of a plurality of bits,
the DA conversion portion of the first stage includes: a plurality of primary voltage supply portions capable of selectively outputting a reference voltage at one of a plurality of predetermined levels; and at least one auxiliary voltage supply portion capable of outputting a reference voltage at an auxiliary level different from the level of the reference voltage output from the primary voltage supply portions, and
the reference voltages output respectively from the primary voltage supply portions and the auxiliary voltage supply portion are controlled so as to be selected based on the digital signal generated by the AD conversion portion, and based on a combination of the outputs from the primary voltage supply portions and the auxiliary voltage supply portion, the analog reference signal in accordance with the digital signal is generated.
2. The pipeline A/D converter according to claim 1 , wherein the reference voltage at the auxiliary level is set at a level between the plurality of levels of the reference voltage to be output from the primary voltage supply portions.
3. The pipeline A/D converter according to claim 2 , wherein the reference voltage to be output from the auxiliary voltage supply portion includes a reference voltage at least one of the plurality of levels of the reference voltage to be output from the primary voltage supply portions, in addition to the reference voltage at the auxiliary level.
4. The pipeline A/D converter according to claim 3 , wherein the primary voltage supply portions output the reference voltage at either of two levels, that is, a high-potential level and a low-potential level, and the reference voltage to be output from the auxiliary voltage supply portion includes the reference voltage at the auxiliary level between the high-potential level and the low-potential level and a reference voltage at either the high-potential level or the low-potential level.
5. The pipeline A/D converter according to claim 4 ,
wherein the first stage is configured to perform A/D conversion of three bits, and
seven primary voltage supply portions and the one auxiliary voltage supply portion are provided.
6. A digital camera comprising the pipeline A/D converter according to claim 1 .