Calibration for amplifier with configurable final output stage

Patent metadata

Field	Value
Publication number	US-9917557-B1
Application number	US-201715488979-A
Country	US
Kind code	B1
Filing date	Apr 17, 2017
Priority date	Apr 17, 2017
Publication date	Mar 13, 2018
Grant date	Mar 13, 2018

Abstract

A method for offset calibration may include decoupling a modulator input of a first path from a first stage output, coupling a second path output to the modulator input, applying a common-mode voltage to a second path input, receiving a calibration signal from the modulator output generated in response to the common-mode voltage, and modifying one or more parameters of the modulator to compensate for an offset between the first path and the second path indicated by the calibration signal. A method for gain calibration may include decoupling a modulator input from a first stage output, decoupling a second path from the first stage output, applying a first test signal to the modulator input, applying a second test signal to a second path input, wherein the second test signal is of opposite phase as the first test signal, coupling a second path output to an amplifier input via a calibration feedback network, receiving a calibration signal from the first stage output generated in response to the first test signal and the second test signal, and modifying one or more parameters of the second path to compensate for a difference in respective gains of the modulator and the second path indicated by the calibration signal.

First claim

What is claimed is:

1. An amplifier comprising:
a plurality of stages comprising at least:
a first stage configured to receive an input signal at an amplifier input and generate at a first stage output an intermediate signal which is a function of the input signal; and
a final output stage configured to generate an output signal which is a function of the intermediate signal at an amplifier output, the final output stage comprising:
a first path comprising:
a modulator having a modulator input for receiving the intermediate signal and configured to generate at a modulator output a modulated signal from the intermediate signal; and
a plurality of output switches configured to generate the output signal from the modulated signal when the first path is selected to generate the output signal; and

a second path having a second path input for receiving the intermediate signal configured to generate at a second path output the output signal from the intermediate signal when the second path is selected to generate the output signal; and

a calibration subsystem configured to, in a calibration mode:
decouple the modulator input from the first stage output;
couple the second path output to the modulator input;
apply a common-mode voltage to the second path input;
receive a calibration signal from the modulator output generated in response to the common-mode voltage; and
modify one or more parameters of the modulator to compensate for an offset between the first path and the second path indicated by the calibration signal.

2. The amplifier of claim 1 , wherein the first path comprises a Class D audio output stage.

3. The amplifier of claim 1 , wherein the second path comprises a Class AB audio output stage.

4. An amplifier comprising:
a plurality of stages comprising at least:
a first stage configured to receive an input signal at an amplifier input and generate at a first stage output an intermediate signal which is a function of the input signal;
a final output stage configured to generate an output signal which is a function of the intermediate signal at an amplifier output, the final output stage comprising:
a first path comprising:
a modulator having a modulator input for receiving the intermediate signal and configured to generate at a modulator output a modulated signal from the intermediate signal; and
a plurality of output switches configured to generate the output signal from the modulated signal when the first path is selected to generate the output signal; and

a second path having a second path input for receiving the intermediate signal configured to generate at a second path output the output signal from the intermediate signal when the second path is selected to generate the output signal; and

a signal feedback network coupled between the amplifier output and the amplifier input; and
a calibration subsystem configured to, in a calibration mode:
decouple the modulator input from the first stage output;
decouple the second path from the first stage output;
apply a first test signal to the modulator input;
apply a second test signal to the second path input, wherein the second test signal is of opposite phase as the first test signal;
receive a calibration signal from the first stage output generated in response to the first test signal and the second test signal; and
modify one or more parameters of the second path to compensate for a difference in respective gains of the first path and the second path indicated by the calibration signal.

5. The amplifier of claim 4 , wherein the first path comprises a Class D audio output stage.

6. The amplifier of claim 4 , wherein the second path comprises a Class AB audio output stage.

7. The amplifier of claim 4 , wherein the calibration subsystem is further configured to, in a second calibration mode:
decouple the modulator input from the first stage output;
couple the second path output to the modulator input;
apply a common-mode voltage to the second path input;
receive a second calibration signal from the modulator output generated in response to the common-mode voltage; and
modify one or more parameters of the modulator to compensate for an offset between the first path and the second path indicated by the second calibration signal.

8. A method comprising, in a calibration mode of an amplifier comprising a plurality of stages comprising at least a first stage configured to receive an input signal at an amplifier input and generate at a first stage output an intermediate signal which is a function of the input signal, and a final output stage configured to generate an output signal which is a function of the intermediate signal at an amplifier output, and wherein the final output stage comprises a first path comprising a modulator having a modulator input for receiving the intermediate signal and configured to generate at a modulator output a modulated signal from the intermediate signal and a plurality of output switches configured to generate the output signal from the modulated signal when the first path is selected to generate the output signal wherein the final output stage further comprises a second path having a second path input for receiving the intermediate signal configured to generate at a second path output the output signal from the intermediate signal when the second path is selected to generate the output signal:
decoupling the modulator input from the first stage output;
coupling the second path output to the modulator input;
applying a common-mode voltage to the second path input;
receiving a calibration signal from the modulator output generated in response to the common-mode voltage; and
modifying one or more parameters of the modulator to compensate for an offset between the first path and the second path indicated by the calibration signal.

9. The method of claim 8 , wherein the first path comprises a Class D audio output stage.

10. The method of claim 8 , wherein the second path comprises a Class AB audio output stage.

11. A method comprising, in a calibration mode of an amplifier comprising a plurality of stages comprising at least a first stage configured to receive an input signal at an amplifier input and generate at a first stage output an intermediate signal which is a function of the input signal and a final output stage configured to generate an output signal which is a function of the intermediate signal at an amplifier output, and wherein the final output stage comprises a first path comprising a modulator having a modulator input for receiving the intermediate signal and configured to generate at a modulator output a modulated signal from the intermediate signal and a plurality of output switches configured to generate the output signal from the modulated signal when the first path is selected to generate the output signal wherein the final output stage further comprises a second path having a second path input for receiving the intermediate signal configured to generate at a second path output the output signal from the intermediate signal when the second path is selected to generate the output signal:
decoupling the modulator input from the first stage output;
decoupling the second path from the first stage output;
applying a first test signal to the modulator input;
applying a second test signal to the second path input, wherein the second test signal is of opposite phase as the first test signal;
receiving a calibration signal from the first stage output generated in response to the first test signal and the second test signal; and
modifying one or more parameters of the second path to compensate for a difference in respective gains of the first path and

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Zhu Lei
• Zhao Xin
• Das Tejasvi
• Morton Alan Mark
• Fei Xiaofan

Classifications

• H03F1/0277 Primary

  Selecting one or more amplifiers from a plurality of amplifiers · CPC title

• H03F2200/321

  Use of a microprocessor in an amplifier circuit or its control circuit · CPC title

• H03F3/72

  Gated amplifiers, i.e. amplifiers which are rendered operative or inoperative by means of a control signal · CPC title

• H03F3/2171

  with field-effect devices (H03F3/2173 - H03F3/2178 take precedence) · CPC title

• H03F3/211 Primary

  using a combination of several amplifiers (H03F3/60 takes precedence) · CPC title