Multi-bit sigma-delta modulator and digital-to-analog converter with one digital-to-analog capacitor

• US 7,388,533 B2
• Filed: 10/27/2006
• Issued: 06/17/2008
• Est. Priority Date: 12/06/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Gyu Hyun, Kim, Jong Dae, Kwon, Chong Ki, Cho, Min Hyung, Kim, Yi Gyeong, Lee, Seung Chul
• Primary Examiner(s): WILLIAMS, HOWARD L
• Application Number:
  US11/588,455
• Publication Number:
  US 20070126615A1
• Time in Patent Office: 599 Days
• Field of Search: 341/143, 341/150
• US Class Current: 341/150
• CPC Class Codes: H03M 3/352 of deviations from the desired transfer characteristic
• CPC Class Codes: H03M 3/424 the quantiser being a multiple bit one
• CPC Class Codes: H03M 3/464 Details of the digital/analogue conversion in the feedback path

Abstract

A digital-to-analog converter (DAC) for a sigma-delta modulator is provided. The DAC has a switched capacitor structure using an operational amplifier (OP amp) and performs a function exceeding 3-level using a switching method employing only one capacitor in single ended form. Thus, DAC non-linearity caused by capacitor mismatching does not occur, and the number of output levels of the DAC is increased. Also, the DAC capacitor may be applied to a general DAC to increase the ratio of DAC output levels to capacitors.

Claims

1. A five-level digital-to-analog converter of a sigma-delta modulator, comprising:

a digital-to-analog converter (DAC) capacitor having a switched capacitor structure using two phases; and

three switches for connecting reference voltages with different polarities to a common terminal of the DAC capacitor when the two phases are converted, the three switches consisting of;

a first switch for connecting a positive reference voltage to the common terminal of the DAC capacitor;

a second switch for connecting a “

0”

reference voltage to the common terminal of the DAC capacitor; and

a third switch for connecting a negative reference voltage to the common terminal of the DAC capacitor;

wherein the reference voltages with different polarities connected to the common terminal of the DAC capacitor are combined according to the two phases to provide five-level output.

2. The five-level digital-to-analog converter according to claim 1, wherein the switch serves to convert the reference voltage applied to the DAC capacitor from a negative reference voltage to “

0”

, from a positive reference voltage to “

0”

, from “

0”

to “

0”

, from the negative reference voltage to the positive reference voltage, and from the positive reference voltage to the negative reference voltage.

3. The five-level digital-to-analog converter according to claim 2, wherein the conversion from “

0”

to “

0”

includes a switching operation corresponding to “

0”

.

4. The five-level digital-to-analog converter according to claim 3, wherein the switching method of the switch is used to implement a DAC with five levels using only one DAC capacitor in single ended form.

5. The five-level digital-to-analog converter according to claim 2, wherein the switching method of the switch is used to implement a DAC with five levels using only one DAC capacitor in single ended form.