Microphone with voltage pump

• US 8,295,512 B2
• Filed: 05/19/2008
• Issued: 10/23/2012
• Est. Priority Date: 12/01/2003
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Deruginsky, Michael, Fuerst, Claus Erdmann, Shajaan, Mohammad, Sassene, Daifi
• Primary Examiner(s): Davetta, Goins
• Assistant Examiner(s): Paul, Disler
• Application Number:
  US12/123,213
• Publication Number:
  US 20080219474A1
• Time in Patent Office: 1,618 Days
• Field of Search: 381 91- 92, 381111-115, 381/122, 381173-174, 381/178, 381/375, 381/95, 330/252, 330/85, 330/96, 330/136
• US Class Current: 381/113
• CPC Class Codes: H02M 3/073 Charge pumps of the Schenkel-type
• CPC Class Codes: H04R 25/407 Circuits for combining signals of a plurality of transducers
• CPC Class Codes: H04R 3/00 Circuits for transducers , loudspeakers or microphones
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

An integrated circuit configured to provide a microphone output signal, comprising: a preamplifier coupled to receive an input signal, generated by either a first microphone member or a second microphone member, where one of the members is movable relative to the other microphone member; a voltage pump to output a pumped voltage; and a low-pass filter coupled to filter the pumped voltage from the voltage pump and to provide a bias voltage to either microphone member.

Claims

1. An integrated circuit configured to provide a microphone output signal, comprising:

a preamplifier coupled to receive an input signal, generated by either a first microphone member or a second microphone member, where one of the members is movable relative to the other microphone member;

a voltage pump to output a pumped voltage; and

a low-pass filter coupled to filter the pumped voltage from the voltage pump and to provide a bias voltage to either the first or second microphone member.

2. An integrated circuit according to claim 1, where the low-pass filter is a first order low-pass filter.

3. An integrated circuit according to claim 1, comprising a circuit which limits the voltage swing at an input of the preamplifier, where the input receives the input signal.

4. An integrated circuit according to claim 1, comprising a capacitor coupled to diminish a DC voltage level at the input of the preamplifier.

5. An integrated circuit according to claim 1, comprising a capacitor coupled serially between the preamplifier and the microphone member generating the input signal.

6. An integrated circuit according to claim 1, comprising a capacitor coupled serially between the member, which is different from the microphone member generating the input signal and a ground reference.

7. An integrated circuit according to claim 1, where the preamplifier is configured to output a signal, which is high-pass filtered by the preamplifier and a filter comprised by the preamplifier.

8. An integrated circuit according to claim 1, where the preamplifier, comprises:

a differential input stage with a first and a second input terminal and an output stage with an output terminal;

a feedback circuit, with a low-pass frequency transfer function, coupled between the output terminal and the first input terminal and integrated on the semiconductor substrate; and

where the second input terminal provides an input for a microphone signal.

9. An integrated circuit according to claim 8, where the feedback circuit is a filter with a transfer function, in the frequency domain, with a zero and a pole;

wherein the zero is located at a higher frequency than the pole.

10. An integrated circuit according to claim 8 where the preamplifier has a transfer function, in the frequency domain, with a zero and a pole;

wherein the pole is located in the range 0.1 Hz to 50 Hz or 0.1 Hz to 100 Hz or 0.1 to 200 Hz.

11. An integrated circuit according to claim 8, where the feedback circuit is a filter which, in the frequency domain, has a relatively high gain level below a transition frequency range and a relatively low gain level above the transition frequency range.

12. An integrated circuit according to claim 11, where the transition frequency range is located below a frequency of about 100 Hz.

13. An integrated circuit according to claim 11, where the transition frequency range is located below a frequency of 40 Hz.

14. An integrated circuit according to claim 1, where the preamplifier outputs an analogue signal;

and

where the integrated circuit comprises an analogue-to-digital converter which is coupled to receive an analogue signal output by the preamplifier.

15. An integrated circuit according to claim 1, where the integrated circuit further is configured with an analogue-to-digital converter;

and

wherein the voltage pump and the analogue-to-digital converter are driven by a common clock-signal.

16. An integrated circuit according to claim 14, where the analogue-to-digital converter is of the sigma delta converter type.

17. An integrated circuit according to claim 1, where the integrated circuit is configured with an oscillator driven voltage pump to provide a bias voltage to either microphone member;

and

where the oscillator is configured to draw substantially equal levels of current across signal cycles provided by the oscillator.

18. An integrated circuit according to claim 17, where the oscillator comprises paths with elements that can be charged with an electrical charge and where the paths are controlled by the oscillator to charge the different elements of the different paths alternately by a current drawn from a common source.

19. An integrated circuit according to claim 1, where the voltage pump has a first pump stage at which an oscillating signal with a voltage pulse level is pumped to a higher voltage pulse level, and a second pump stage at which a voltage level is pumped to a higher level by means of a circuit operating on the oscillator signal, provided at the first stage, with the higher voltage pulse level.

20. An integrated circuit according to claim 1, where the integrated circuit comprises:

a first portion configured with a circuit component layout for electrical operation at or below a nominal voltage level and a second portion configured with a circuit component layout for electrical operation above the nominal voltage.

21. An integrated circuit according to claim 19, where an output signal of the first voltage pump stage is provided as a feedback signal to a circuit which maintains a fixed voltage pulse level of the signals output from the first pump stage.

22. An integrated circuit according to claim 1, where the voltage pump has a first pump stage providing an intermediate voltage and a second pump stage providing the pumped voltage from the intermediate bias voltage;

and where the second pump stage comprises a voltage pump configured as a Dickson converter.

23. An integrated circuit according to claim 22, where an output signal of the Dickson converter is provided as a feedback signal to a circuit which provides a regulated voltage pulse level of the signals output from the voltage converter.

24. An integrated circuit according to claim 1, where multiple voltage converters are cascaded to provide the bias voltage, and where a further voltage converter, which matches the first converter in the cascade, is coupled to receive the same signal as the first converter and to provide a feedback signal to a circuit which maintains a fixed voltage level of the signals output from the further voltage converter.

25. An integrated circuit according to claim 1, where the voltage pump comprises capacitors implemented as Metal capacitors.

26. An integrated circuit according to claim 1, where the voltage pump comprises diodes implemented as Poly-diodes.

27. An integrated circuit according to claim 1, where the voltage pump comprises diodes implemented as diffusion diodes in an N-well.

28. A microphone comprising an integrated circuit according to claim 1.

29. A microphone according to claim 28, where the microphone is a condenser microphone.

30. A microphone according to claim 28, where the microphone is a MEMS microphone.

31. The integrated circuit according to claim 1, wherein the preamplifier, voltage pump and at least a portion of the low-pass filter are embodied on a single semiconductor substrate for integration with a microphone element.

32. The integrated circuit according to claim 1, wherein the preamplifier, voltage pump and at least a portion of the low-pass filter are embodied on a single semiconductor substrate for integration with a microphone element in a microphone cartridge.