System and method for a PCM interface for a capacitive signal source

Patent metadata

Field	Value
Publication number	US-9467774-B2
Application number	US-201213370920-A
Country	US
Kind code	B2
Filing date	Feb 10, 2012
Priority date	Feb 10, 2012
Publication date	Oct 11, 2016
Grant date	Oct 11, 2016

Abstract

In accordance with embodiment, a method includes amplifying signal provided by a microphone to form an amplified signal. The method also includes converting the amplified signal into a frequency-based signal having a frequency dependent on an amplitude of the amplified signal. The frequency-based signal is converted into a pulse code modulated bitstream.

First claim

What is claimed is:

1. A method comprising:
amplifying a signal provided by a microphone to form an amplified signal;
converting the amplified signal into a frequency-based signal having a frequency dependent on an amplitude of the amplified signal; and
converting the frequency-based signal into a pulse code modulated (PCM) bitstream using a sigma-delta converter, wherein the sigma-delta converter is configured to provide a PCM output code proportional to a frequency of the frequency-based signal, wherein the sigma-delta converter comprises a loop filter having a first input coupled to the frequency-based signal, a second voltage controlled oscillator (VCO) having an input coupled to an output of the loop filter, and a frequency-to-PCM circuit coupled to an output of the second VCO, and wherein an output of the frequency-to-PCM circuit is coupled to a second input of the loop filter.

2. The method of claim 1 , wherein amplifying the signal provided by the microphone comprises amplifying an output of a MEMS microphone.

3. The method of claim 1 , wherein converting the amplified signal into the frequency-based signal comprises coupling the amplified signal to an input of a first voltage controlled oscillator (VCO).

4. A circuit comprising:
a voltage-to-frequency converter having an input configured to be coupled to a microphone; and
a frequency-to-PCM converter having an input coupled to an output of the voltage to frequency converter, wherein the frequency-to-PCM converter comprises a sigma-delta converter, wherein the sigma-delta converter is configured to provide a PCM output code proportional to a frequency of a signal provided by the voltage-to-frequency converter, wherein the sigma-delta converter comprises a loop filter having a first input coupled to the input of the frequency-to-PCM converter, a voltage controlled oscillator (VCO) having an input coupled to an output of the loop filter, and a frequency-to-PCM circuit coupled to an output of the VCO, and wherein an output of the frequency-to-PCM circuit is coupled to a second input of the loop filter.

5. The circuit of claim 4 , further comprising the microphone.

6. The circuit of claim 4 , wherein the microphone is a MEMS microphone.

7. The circuit of claim 4 , wherein the voltage-to-frequency converter and the frequency-to-PCM converter are disposed on an integrated circuit.

8. The circuit of claim 4 , wherein:
the voltage-to-frequency converter comprises a second voltage controlled oscillator (VCO).

9. A microphone module comprising:
an acoustic enclosure;
a microphone disposed within the acoustic enclosure; and
an audio conversion circuit coupled to an output of the microphone, the audio conversion circuit comprising:
a voltage-to-frequency converter coupled to the output of the microphone, and
a frequency-to-PCM converter coupled to an output of the voltage-to-frequency converter, wherein the frequency-to-PCM converter comprises a sigma-delta converter, wherein the sigma-delta converter is configured to provide a PCM output code proportional to a frequency of a signal provided by the voltage-to-frequency converter, wherein the sigma-delta converter comprises a loop filter having a first input coupled to an input of the frequency-to-PCM converter, a voltage controlled oscillator (VCO) having an input coupled to an output of the loop filter, and a frequency-to-PCM circuit coupled to an output of the VCO, and wherein an output of the frequency-to-PCM circuit is coupled to a second input of the loop filter.

10. The microphone module of claim 9 , further comprising an output port coupled to an output of the frequency-to-PCM converter.

11. The microphone module of claim 9 , wherein the microphone comprises a MEMS microphone.

Assignees

• Hammerschmidt Dirk
• Kropfitsch Michael
• Wiesbauer Andreas
• Infineon Technologies Ag

Inventors

• Hammerschmidt Dirk
• Kropfitsch Michael
• Wiesbauer Andreas

Classifications

• H03M3/424

  the quantiser being a multiple bit one · CPC title

• H04R3/00 Primary

  Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) · CPC title

• H04R2460/03

  Aspects of the reduction of energy consumption in hearing devices · CPC title

• H04R19/005

  using semiconductor materials · CPC title

• H04R19/016

  for microphones · CPC title