Gain or input volume controller and method utilizing a modified R2R ladder network

• US 7,162,029 B2
• Filed: 05/29/2003
• Issued: 01/09/2007
• Est. Priority Date: 05/29/2003
• Status: Expired due to Fees

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John Laurence, Hong, Hua, Subramoniam, Krishnan, Datar, Rajendra, Soman, Manoj
• Primary Examiner(s): Tsang; Fan
• Assistant Examiner(s): Singh; Ramnandan
• Application Number:
  US10/447,606
• Publication Number:
  US 20040240918A1
• Time in Patent Office: 1,321 Days
• Field of Search: 379/399.02, 341/144
• US Class Current: 379/399.02
• CPC Class Codes: H03M 1/68 with conversions of different sensitivity, i.e. one conversion relating to the more significant digital bits and another conversion to the less significant bits
• CPC Class Codes: H03M 1/785 using resistors, i.e. R-2R ladders

Abstract

A gain or input volume controller and method includes a modified R2R ladder network having a number of R2R branches, switches coupled respectively to the R2R branches, and a switch controller for respectively controlling the switches to control and provide an overall gain value for a signal. The switch controller further includes a mapper for mapping a gain control signal to the switches wherein the gain control signal respectively activates or deactivates the switches. A fine gain control stage provides a fine gain control of the overall gain value. A coarse gain control stage is coupled to the fine gain control stage. The coarse gain control stage includes the modified R2R ladder network and provides a coarse gain control of the overall gain value.

Claims

1. A gain controller, comprising:

an input terminal for receiving a time-varying input signal;

another input terminal for receiving a digital gain control signal;

a modified R2R ladder network coupled to the input terminal for receiving the time-varying input signal and to the another input terminal for receiving the digital gain control signal;

a mixer coupled to the modified R2R ladder network wherein the mixer produces an output signal, which is the time-varying input signal scaled by a gain factor, and the mixer performs a current-to-voltage conversion; and

wherein the modified R2R ladder network further comprises;

resistors for R2R branches of the modified R2R ladder network;

switches coupled to the R2R branches; and

a switch controller for controlling the switches in conformity with the digital gain control signal; and

wherein the mixer further comprises;

an operational amplifier having one input coupled to a common mode voltage and an output that provides the output signal; and

a feedback resistor having one end coupled to another input of the operational amplifier and another end coupled to the output of the operational amplifier; and

wherein an output of the modified R2R ladder network is a current fed into the feedback resistor and the another input of the operational amplifier.

2. The gain controller according to claim 1, wherein each of the R2R branches comprises:

a resistor having a resistor value R wherein the resistor is one among a series of resistors in the modified R2R ladder network; and

another resistor having a resistor value 2R, which is twice the resistor value R, wherein one end of the another resistor is coupled to an end of the resistor and another end of the another resistor is coupled to a common mode or an output path providing the output signal.

3. The gain controller according to claim 2, wherein:

a respective one of the switches is coupled between another end of the another resistor and a common mode; and

a respective another of the switches is coupled between the another end of the another resistor and the output path that provides the output signal.

4. The gain controller according to claim 1, wherein the switch controller further comprises:

a mapper for mapping the digital gain control signal to the switches wherein the digital gain control signal respectively activates or deactivates the switches.

5. The gain controller according to claim 1, further comprising:

a fine gain control stage for providing a fine gain control of the output signal; and

a coarse gain control stage coupled to the fine gain control stage, wherein the coarse gain control stage includes the R2R ladder network and provides a coarse gain control of the output signal.

6. The gain controller according to claim 5, wherein the coarse gain control stage further comprises:

the R2R ladder network having a number of R2R branches wherein each of the R2R branches has a resistor having a resistor value R wherein the resistor is one among a series of resistors in the modified R2R ladder network and another resistor having a resistor value 2R, which is twice the resistor value R, wherein one end, of the another resistor is coupled to an end of the resistor and another end of the another resistor is coupled to a common mode or an output path, and a respective one of the switches is coupled between the another end of the another resistor and a common mode and a respective another of the switches is coupled between the another end of the another resistor and an output path that provides the output signal;

a first branch coupled at an input end of the R2R ladder network wherein the first branch includes a first additional resistor and a first additional switch coupled together in series and wherein one end of the first branch is coupled to an input end of an input path and another end of the first branch is coupled to the common mode; and

a second branch coupled to an output end of the R2R ladder network wherein the second branch includes a second additional resistor and a second additional switch coupled together in series and wherein one end of the second branch is coupled to an output end of the output path and another end of the second branch is coupled to the common mode.

7. The gain controller according to claim 5, wherein the fine gain control stage further comprises:

one resistor coupled to a series of resistors in the R2R ladder network;

a selectable resistor path having resistors coupled together in series and additional switches wherein one end of the selectable resistor path is coupled to an end of the one resistor and another end of the selectable resistor path is coupled to a common mode and wherein a respective one of the additional switches is coupled between each node of the resistors in series and the common mode and wherein each of the respective one of the additional switches when activated provides a different resistance for the selectable resistor path.

8. The gain controller according to claim 5, further comprising:

a resistor chain coupled to an input end of the fine gain control stage wherein the resistor chain further comprises;

one resistor coupled to a series of resistors in the modified R2R ladder network; and

a selectable resistor path having resistors coupled together in series and additional switches wherein one end of the selectable resistor path is coupled to an end of the one resistor and another end of the selectable resistor path is coupled to a common mode and wherein a respective one of the additional switches is coupled between each node of the resistors in series and the common mode and wherein each of the respective one of the switches when activated provides a different resistance for the selectable resistor path.

9. The gain controller according to claim 5, wherein one portion of the digital gain control signal controls the fine gain control stage and another portion of the digital gain control signal controls the coarse gain control stage.

10. The gain controller according to claim 1, wherein:

the output signal is an audio signal; and

the gain controller is a volume controller that Is able to couple to an input of an analog mixer and control a volume level during a playback operation of the audio signal.

11. The gain controller according to claim 1, wherein:

the output signal is an audio signal; and

the gain controller is able to couple in a feedback path of an operational amplifier and control a gain level during a capture operation of the audio signal.

12. A method for controlling gain of a signal by a gain controller, comprising:

inputting a time-varying input signal and a digital gain control signal into a modified R2R ladder network having resistors that provide R2R branches, switches coupled to the R2R branches, and a switch controller for controlling the switches in conformity with the digital gain control signal; and

producing an output signal by a mixer coupled to the modified R2R ladder network wherein the output signal is the time-varying input signal scaled by a gain factor and wherein the mixer performs a current-to-voltage conversion and wherein the mixer further comprises an operational amplifier having one input coupled to a common mode voltage and an output that provides the output signal, and a feedback resistor having one end coupled to another input of the operational amplifier and another end coupled to the output of the operational amplifier; and

wherein an output of the modified R2R ladder network is a current fed into the feedback resistor and the another input of the operational amplifier.

13. The method according to claim 12, wherein inputting a time-varying Input signal and a digital gain control signal into a modified R2R ladder network further comprises:

providing for each of the R2R branches a resistor having a resistor value R, another resistor having a resistor value 2R, which is twice the resistor value R, a respective one of the switches coupled between the another resistor and a common mode, and a respective another of the switches coupled between the another resistor and an output path that provides the output signal; and

activating the respective one of the switches and the respective another of the switches to activate the respective each of the R2R branches.

14. The method according to claim 12, further comprising:

mapping the digital gain control signal to the switches wherein the digital gain control signal respectively activates or deactivates the switches.

15. The method according to claim 12, further comprising:

fine gain controlling the output signal; and

coarse gain controlling the output signal.

16. The method according to claim 15, wherein:

fine gain controlling further comprises utilizing one portion of the digital gain control signal; and

coarse gain controlling further comprises utilizing another portion of the digital gain control signal.

17. The method according to claim 12, wherein:

the output signal is an audio signal and the gain controller is a volume controller that is able to couple to an input of an analog mixer; and

producing an output signal further comprises controlling a volume level during a playback operation of the audio signal.

18. The method according to claim 12, wherein:

the output signal is an audio signal and the gain controller is able to couple in a feedback path of an operational amplifier; and

producing an output signal further comprises controlling a gain level during a capture operation of the audio signal.

19. A codec for coding and decoding signals, comprising:

a clock generator system for providing an operating clock signal for the codec;

a digital interface block having at least registers and a codec link interface for coupling to a codec controller wherein the clock generator system is coupled to the digital interface block;

a digital input/output interface block for digitally interfacing with input and output devices wherein the digital input/output interface block is coupled to the digital interface block;

an analog interface block having at least an analog-to-digital converter, an input multiplexer, an input mixer, an output mixer, a digital-to-analog converter wherein the analog interface block is coupled to the digital interface block, a volume controller coupled to an input of the digital-to-analog converter wherein the volume controller has an input terminal for receiving a time-varying input signal from the digital-to-analog converter, another input terminal for receiving a digital gain control signal, a modified R2R ladder network coupled to the input terminal for receiving the time-varying input signal and to the another input terminal for receiving the digital gain control signal wherein the modified R2R ladder network has resistors that provide R2R branches, switches coupled to the R2R branches, and a switch controller for controlling the switches in conformity with the digital gain control signal, and a mixer coupled to the modified R2R ladder network wherein the mixer produces an output signal, which is the time-varying input signal scaled by a gain factor and the mixer performs a current-to-voltage conversion and wherein the mixer further comprises an operational amplifier having one input coupled to a common mode voltage and an output that provides an output signal, and a feedback resistor having one end coupled to another input of the operational amplifier and another end coupled to the output of the operational amplifier; and

wherein an output of the modified R2R ladder network is a current fed into the feedback resistor and the another input of the operational amplifier; and

a sample rate conversion system coupled between the digital interface block and the analog interface block to convert between respective sample rates of the digital interface block and the analog interface block.

20. The codec according to claim 19, further comprising:

a gain controller coupled to an input of the analog-to-digital converter wherein the gain controller has another modified R2R ladder network having a number of other R2R branches wherein other resistor values of the gain controller are selected, other switches coupled respectively to the other R2R branches, and another switch controller for respectively controlling the other switches to control and provide a gain value for a signal to be converted by the analog-to-digital converter.

21. The codec according to claim 20, wherein each of the other R2R branches has a resistor having a resistor value R wherein the resistor is one among a series of resistors in the modified R2R ladder network and another resistor having a resistor value 2R, which is twice the resistor value R, wherein one end of the another resistor is coupled to an end of the resistor and another end of the another resistor is coupled to a common mode and a respective one of the switches is coupled between the another end of the another resistor and a common mode and a respective another of the switches is coupled between the another end of the another resistor and an output path that provides the output signal.

22. The codec according to claim 19, wherein each of the R2R branches has a resistor having a resistor value R wherein the resistor is one among a series of resistors in the modified R2R ladder network and another resistor having a resistor value 2R, which is twice the resistor value R, wherein one end of the another resistor is coupled to an end of the resistor and another end of the another resistor is coupled to a common mode and a respective one of the switches is coupled between the another end of the another resistor and a common mode and a respective another of the switches is coupled between the another end of the another resistor and an output path that provides the output signal.