Apparatus and method for testing a capacitive transducer and/or associated electronic circuitry

Patent metadata

Field	Value
Publication number	US-9575116-B2
Application number	US-201414156723-A
Country	US
Kind code	B2
Filing date	Jan 16, 2014
Priority date	Dec 30, 2008
Publication date	Feb 21, 2017
Grant date	Feb 21, 2017

Abstract

A method of testing a capacitive transducer circuit, for example a MEMS capacitive transducer, by applying a test signal via one or more capacitors provided in the transducer circuit.

First claim

What is claimed is:

1. An integrated circuit for biasing a MEMS capacitive transducer having a MEMS capacitor, the integrated circuit comprising:
a charge pump comprising an input for receiving an input voltage and an output for outputting an output voltage for biasing a first plate of the MEMS capacitor, wherein the output of said charge pump is coupled to a first circuit node;
a first capacitor having a first plate and a second plate, wherein said first plate of the first capacitor is connected to said first circuit node; and
switching circuitry coupled to the second plate of the first capacitor for selectively coupling a test signal to the first node and to the first plate of the MEMS capacitor via the first capacitor during a test mode of operation.

2. An integrated circuit as claimed in claim 1 wherein the switching circuitry is operable to selectively coupling the second plate of the first capacitor to a reference voltage during a non-test mode of operation.

3. An integrated circuit as claimed in claim 1 further comprising a second capacitor having a first plate connected to said first circuit node and a second plate connected to a reference voltage.

4. An integrated circuit as claimed in claim 3 wherein said switching circuitry is operable to connect the first capacitor in parallel with the second capacitor during a non-test mode of operation.

5. An integrated circuit as claimed in claim 3 wherein the capacitance of said first capacitor is less than the capacitance of said second capacitor.

6. An integrated circuit as claimed in claim 1 comprising at least one additional capacitor, wherein each said additional capacitor has a first plate and a second plate, wherein said first plate is connected to said first circuit node and said second plate is connected to said switching circuitry.

7. An integrated circuit as claimed in claim 6 wherein said switching circuitry is operable to selectively couple the test signal to the first node via a selected number of one or more of the first capacitor and said additional capacitors.

8. An integrated circuit as claimed in claim 6 wherein said first capacitor has a different value of capacitance to said at least one additional capacitor.

9. An integrated circuit as claimed in claim 1 comprising a signal source for generating said test signal.

10. An integrated circuit as claimed in claim 9 wherein said signal source is configured to generate said test signal with at least one of a variable amplitude and a variable frequency.

11. An integrated circuit as claimed in claim 1 comprising a diode between said charge pump output and said first node.

12. An apparatus comprising an integrated circuit as claimed in claim 1 and a MEMS capacitive transducer connected to said first circuit node.

13. An apparatus as claimed in claim 12 wherein said MEMS capacitive transducer is formed on a separate substrate to said integrated circuit.

14. An electronic device comprising an integrated circuit as claimed in claim 1 .

15. An electronic device as claimed in claim 14 wherein said electronic device is at least one of: a consumer device; a medical device; an automotive device; a portable device; an audio player; a laptop; a mobile telephone; and a computing device.

16. An integrated circuit for applying a bias voltage to a MEMS capacitive transducer comprising:
a bias source for generating a bias voltage, the output of the bias source being coupled to a first node;
a first reservoir capacitor; and
switch circuitry,
wherein said first reservoir capacitor is coupled between said first node and said switch circuitry; and
wherein said switch circuitry is operable:
in a non-test mode to couple said first reservoir capacitor to a reference voltage so that the first capacitor maintains the bias voltage at the first node; and
in a test mode of operation to couple said first reservoir capacitor to a test signal input so as to couple a varying test signal to the first node and the MEMS capacitive transducer via the first reservoir capacitor.

17. An integrated circuit as claimed in claim 16 further comprising a second capacitor coupled between said first node and said reference voltage such that, in said non-test mode, said first and second capacitors collectively maintain the bias voltage at the first node.

18. An integrated circuit as claimed in claim 16 wherein said bias source comprises a charge pump for receiving an input voltage and generating an output voltage as said bias voltage.

19. An integrated circuit comprising:
a MEMS capacitive transducer;
a first capacitor having a first plate and a second plate, wherein said first plate of said first capacitor is electrically connected to said MEMS capacitive transducer; and
switch circuitry electrically connected to said second plate of said first capacitor, wherein said switch circuitry is operable:
in a non-test mode to couple said first capacitor to a fixed reference voltage so that the first capacitor maintains a first voltage; and
in a test mode of operation to couple said first capacitor to a test signal input so as to couple a varying test signal to the MEMS capacitive transducer via the first capacitor.

20. An integrated circuit as claimed in claim 19 further comprising a bias source for generating a bias voltage at bias node wherein said first plate of the first capacitor is electrically connected to said bias node.

Assignees

• Wolfson Microelectronics Plc
• Cirrus Logic Inc

Inventors

• Steele Colin Findlay
• Pennock John L

Classifications

• G01R31/2884 Primary

  using dedicated test connectors, test elements or test circuits on the IC under test (G01R31/2855 takes precedence) · CPC title

• H04R29/004 Primary

  for microphones (H04R29/007 takes precedence) · CPC title

• H04R19/005

  using semiconductor materials · CPC title

• H04R2201/003

  Mems transducers or their use · CPC title

• B81B7/008

  MEMS characterised by an electronic circuit specially adapted for controlling or driving the same (B81B7/0087 takes precedence; arrangements for starting, regulating, braking, or otherwise controlling an actuator H02N; control arrangements or circuits for visual indicators G09G3/00) · CPC title