Sensor data acquisition system with integrated power management

Patent metadata

Field	Value
Publication number	US-9634567-B2
Application number	US-201514624106-A
Country	US
Kind code	B2
Filing date	Feb 17, 2015
Priority date	Feb 17, 2015
Publication date	Apr 25, 2017
Grant date	Apr 25, 2017

Abstract

A microelectromechanical systems (MEMS) sensor with an integrated power management system that performs analog to digital conversion of weak signals is provided. The MEMs sensor can include a switching regulator that steps a supply voltage down to a voltage appropriate for an analog to digital converter (A/D converter). A timing circuit is provided to generate a clock frequency for the switching regulator and the A/D converter such that the clock frequencies are harmonically related. The frequency of the voltage ripples formed by the switching regulator will match the clock frequency provided to the switching regulator. When the sampling frequency of the A/D converter is harmonically related to the voltage ripple frequencies, the aliasing frequency will fall outside a range of frequencies associated with the analog signal.

First claim

What is claimed is:

1. An application specific integrated circuit, comprising:
a switching regulator that receives a power supply at a first voltage and outputs a power output at a second voltage different than the first voltage;
an analog to digital converter that converts an analog electrical signal into a digital signal, wherein the analog to digital converter receives the power output via the switching regulator; and
a timing circuit that controls a switching frequency of the switching regulator and a sampling frequency of the analog to digital converter such that the switching frequency and sampling frequency are harmonically related.

2. The application specific integrated circuit of claim 1 , further comprising:
a low dropout regulator that regulates the second voltage of the power output.

3. The application specific integrated circuit of claim 1 , further comprising:
a controller that receives feedback based on the power output and manages the switching regulator to adjust the second voltage of the power output.

4. The application specific integrated circuit of claim 3 , wherein the controller monitors the power supply, and changes a conversion ratio of the switching regulator in response to a change in the first voltage of the power supply.

5. The application specific integrated circuit of claim 1 , wherein the timing circuit receives a timing signal from an oscillator.

6. The application specific integrated circuit of claim 1 , wherein the timing circuit receives the timing signal from an external clock.

7. The application specific integrated circuit of claim 1 , wherein the timing circuit selects timing signals from at least one of an external clock and an oscillator.

8. The application specific integrated circuit of claim 1 , wherein an aliasing frequency formed by a function of the sampling frequency and the switching frequency is outside a predetermined range of frequencies associated with the analog electrical signal.

9. The application specific integrated circuit of claim 1 , further comprising a transducer.

10. The application specific integrated circuit of claim 9 , wherein the transducer can be any one of a MEMs acoustic sensor, a MEMS accelerometer, a pressure sensor and a MEMS gyroscope.

11. The application specific integrated circuit of claim 1 , wherein the switching regulator is an inductive switching regulator.

12. The application specific integrated circuit of claim 1 , wherein the switching regulator is a switched capacitors voltage converter.

13. The application specific integrated circuit of claim 1 , wherein the switching regulator operates in an open loop.

14. The application specific integrated circuit of claim 1 , wherein the switching regulator uses a constant-frequency modulation scheme.

15. The application specific integrated circuit of claim 14 , wherein the constant-frequency modulation is digital capacitance modulation.

16. The application specific integrated circuit of claim 1 , wherein the switching regulator uses a narrow band frequency modulation scheme.

17. The application specific integrated circuit of claim 16 , wherein the narrow band frequency modulation scheme is a pulse width modulation scheme.

18. The application specific integrated circuit of claim 1 , wherein the switching frequency is an integer multiple of the sampling frequency.

19. The application specific integrated circuit of claim 1 , wherein the sampling frequency is an integer multiple of the switching frequency.

20. A method, comprising:
converting a voltage of a power input from a power supply that has a first voltage to a converted power output that has a second voltage, wherein the converting is based on a switching frequency;
generating an analog electrical signal based on input received via a transducer;
sampling the analog electrical signal at a sampling frequency and generating a digital signal based on the sampling; and
generating a timing signal that determines the switching frequency and the sampling frequency such that the switching frequency and the sampling frequency are harmonically related.

21. The method of claim 20 , further comprising:
adjusting the converted power output to a third voltage with a low dropout regulator.

22. The method of claim 20 , further comprising:
measuring the second voltage of the converted output, and adjusting the converting based on a results of the measuring.

23. The method of claim 20 , further comprising:
monitoring the first voltage of the power input and adjusting a conversion ratio of a switching regulator in response to a change in the first voltage satisfying a predetermined criterion.

24. The method of claim 20 , further comprising:
generating the timing signal based on an oscillator.

25. The method of claim 20 , further comprising:
generating the timing signal based on an external clock.

26. The method of claim 20 , wherein the determining the switching frequency and the sampling frequency further comprises:
setting a ratio of switching frequency to sampling frequency such that aliasing of a signal spectrum of the analog electrical signal results in a direct current offset.

27. The method of claim 20 , setting a ratio of switching frequency to sampling frequency such that an aliasing frequency formed by a function of the sampling frequency and the switching frequency is outside a predetermined range of frequencies associated with the analog electrical signal.

28. The method of claim 20 , wherein the switching frequency is an integer multiple of the sampling frequency.

29. The method of claim 20 , wherein the sampling frequency is an integer multiple of the switching frequency.

30. A micro-electromechanical systems (MEMS) sensor comprising:
a transducer that generates an analog electrical signal based on input energy;
a switching regulator that receives a power supply at a first voltage and outputs a power output at a second voltage different than the first voltage;
a timing circuit that controls a switching frequency of the switching regulator and generates a clock output for synchronous sampling, where a sampling frequency of the clock output is such that the switching frequency is an integer multiple of the sampling frequency; and
a pair of ports to output the clock output and the analog electrical signal.

31. The MEMs sensor of claim 30 , further comprising:
a controller that receives feedback based on the power output and manages the switching regulator to adjust the second voltage of the power output.

32. The MEMs sensor of claim 30 , wherein the timing circuit determines a ratio of switching frequency to sampling frequency such that aliasing of a signal spectrum of the analog electrical signal is a direct current offset.

Assignees

• Invensense Inc

Inventors

• Oliaei Omid

Classifications

• G01P2015/0865

  using integrated signal processing circuitry · CPC title

• G01P15/08

  with conversion into electric or magnetic values · CPC title

• H02M3/07

  using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} · CPC title

• G01D11/00

  Component parts of measuring arrangements not specially adapted for a specific variable (G01D13/00, G01D15/00 take precedence) · CPC title

• G01L9/00

  Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements {(G01L11/004 takes precedence)}; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means (measuring differences of two or more pressure values G01L13/00; measuring two or more pressure values simultaneously G01L15/00) · CPC title