Analog-to-digital converter

1. An analog-to-digital converter (ADC), comprising:

a coarse ADC that receives an analog input voltage, generates a first digital signal based on the analog input voltage using a successive approximation register (SAR) method, and outputs a residual voltage remaining after the first digital signal is generated;

an amplifier that receives the residual voltage and a test voltage, generates a residual current by amplifying the residual voltage by a predetermined gain, and generates a test current by amplifying the test voltage by the gain;

a fine ADC that receives the residual current, and generates a second digital signal based on the residual current using the SAR method; and

an auxiliary path that receives the test current, and generates a gain correction signal based on the test current,

wherein the gain of the amplifier is adjusted based on the gain correction signal.

2. The ADC of claim 1 , further comprising:

a selector that outputs one of the residual voltage and the test voltage to the amplifier in response to a selection signal,

wherein the amplifier receives the residual voltage from the selector and converts the residual voltage into the residual current, and then receives the test voltage from the selector and converts the test voltage into the test current.

3. The ADC of claim 1 , wherein the fine ADC comprises:

a first current digital-to-analog converter (IDAC) that outputs a differential voltage determined by a difference between the residual current and a reference current;

a first comparator that compares the differential voltage and outputs a result of the comparison; and

an SAR logic that outputs a digital signal based on the result of the comparison,

wherein the auxiliary path comprises a second IDAC and a second comparator, and the second IDAC and the second comparator have a same configuration as the first IDAC and the first comparator, respectively.

4. The ADC of claim 1 , wherein the amplifier converts the residual voltage into the residual current using a first switched current sampler, and converts the test voltage into the test current using a second switched current sampler.

5. The ADC of claim 1 , wherein the fine ADC comprises:

a first current digital-to-analog converter (IDAC) that outputs a first differential voltage determined by a difference between the residual current and a reference current;

a comparator that compares the first differential voltage, and outputs a result of the comparison; and

an SAR logic that outputs a third digital signal based on the result of the comparison,

wherein the auxiliary path comprises a second IDAC that outputs a second differential voltage determined by a difference between the test current and the reference current,

wherein the first IDAC and the second IDAC share the comparator.

6. The ADC of claim 5 , wherein the first IDAC and the second IDAC have a same configuration.

7. The ADC of claim 5 , further comprising:

a selector that outputs one of the first differential voltage and the second differential voltage to the comparator in response to a selection signal.

8. An analog-to-digital converter (ADC), comprising:

a coarse ADC that samples an analog input voltage for a first period, generates a first digital signal based on the analog input voltage using a successive approximation register (SAR) method for a second period, and outputs a residual voltage remaining after the first digital signal is generated;

an amplifier that receives the residual voltage for a third period, and generates a residual current by amplifying the residual voltage by a predetermined gain;

a fine ADC that receives the residual current for a fourth period, and generates a second digital signal based on the residual current using the SAR method; and

an auxiliary path that receives a test current and generates a gain correction signal based on the test current,

wherein the gain of the amplifier is adjusted for the fourth period in which the fine ADC generates the second digital signal based on the residual current.

9. The ADC of claim 8 , wherein, after the third period in which the amplifier generates the residual current by amplifying the residual voltage, the amplifier receives a test voltage and generates the test current by amplifying the test voltage by the gain.

10. The ADC of claim 9 , wherein the auxiliary path compares a full scale of the test current with a full scale of a reference current for the fourth period, and generates the gain correction signal such that the full scale of the test current and the full scale of the reference scale match.

11. The ADC of claim 9 , wherein the amplifier samples the test current in response to a correction sampling clock for the fourth period,

wherein the auxiliary path compares a differential voltage determined by a difference between the test current and a reference current in response to a correction comparison clock for the fourth period, and outputs a result of the comparison as the gain correction signal.

12. The ADC of claim 8 , wherein the coarse ADC receives a following analog input voltage during the fourth period, and generates a third digital signal based on the following analog input voltage using the SAR method.

13. An analog-to-digital converter (ADC), comprising:

a coarse ADC that receives an analog input voltage, generates a first digital signal based on the analog input voltage using a successive approximation register (SAR) method, and outputs a residual voltage remaining after the first digital signal is generated;

a test voltage generator that outputs a test voltage;

a selector that outputs one of the residual voltage and the test voltage in response to a selection signal;

an amplifier that receives the residual voltage and the test voltage from the selector, generates a first residual current by amplifying the residual voltage by a predetermined gain, and generates a test current by amplifying the test voltage by the gain;

a fine ADC that receives the first residual current, generates a second digital signal based on the first residual current using the SAR method, and outputs a second residual current remaining after the second digital signal is generated;

an auxiliary path that receives the test current, and generates a gain correction signal based on the test current,

wherein the gain of the amplifier is adjusted based on the gain correction signal; and

a gain correction circuit that outputs a control signal that controls the amplifier such that the amplifier corrects the gain based on the gain correction signal,

wherein regardless of a time at which the fine ADC converts the first residual current into the second digital signal, the auxiliary path generates the gain correction signal based on the test current.

14. The ADC of claim 13 , wherein the auxiliary path generates the gain correction signal based on the test current while the fine ADC converts the first residual current into the second digital signal.

15. The ADC of claim 13 , wherein the auxiliary path compares a full scale of the test current with a full scale of a reference current, and generates the gain correction signal such that the full scale of the test current and the full scale of the reference current match.