Resonant Signal Sensing Circuit Having a Low Power Mode

• US 20140176115A1
• Filed: 12/19/2013
• Published: 06/26/2014
• Est. Priority Date: 01/03/2012
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Pflum, Marty
• Granted Patent: US 9,689,724 B2
• Time in Patent Office: Days
• US Class Current: 324/76.11
• CPC Class Codes: G01D 4/02 Details
• CPC Class Codes: G01F 1/075 with magnetic or electromagnetic coupling to the indicating device
• CPC Class Codes: G01F 1/115 with magnetic or electromagnetic coupling to the indicating device

Abstract

An apparatus includes a sensor circuit to receive a varying signal at an input of the apparatus. The sensor circuit provides a sensor signal corresponding to a measurement of the varying signal. The apparatus further includes a timer circuit to generate a signal at various intervals of a plurality of intervals and a controller coupled to the sensor circuit. The controller has a first power mode and a second power mode, where the first power mode has a lower power consumption than the second power mode. The controller enters the second power mode in response to the signal from the timer circuit. The controller enables the sensor circuit, captures a plurality of measurements of the varying signal, and returns to the first power mode.

Claims

1. An apparatus comprising:

a sensor circuit coupled to receive a varying signal at an input of the apparatus, the sensor circuit to provide a sensor signal corresponding to a measurement of the varying signal;

a timer circuit to generate a signal at various intervals of a plurality of intervals; and

a controller coupled to the sensor circuit and having a first power mode and a second power mode, the first power mode having a lower power consumption than the second power mode, the controller to enter the second power mode in response to the signal from the timer circuit and to;

enable the sensor circuit;

capture a plurality of measurements of the varying signal; and

return to the first power mode.

2. The apparatus of claim 1, further comprising:

a pulse generator to provide an excitation signal to an output of the apparatus at a first point in time; and

wherein the sensor circuit receives the varying signal in response to the excitation signal at a second point in time.

3. The apparatus of claim 2, wherein the controller provides a wake up signal to the sensor circuit and the pulse generator at the first point in time.

4. The apparatus of claim 2, wherein:

the timer circuit comprises a real time clock (RTC); and

the first point in time and the second point in time are separated by a pre-determined number of clock cycles of the RTC.

5. The apparatus of claim 1, further comprising a resonant circuit having a first node that is coupled to the sensor circuit, the resonant circuit to produce the varying signal, the resonant circuit including an inductor-capacitor (LC) tank circuit.

6. The apparatus of claim 1, further comprising a sensing circuit to produce the varying signal, the sensing circuit comprising at least one of a capacitive sensing circuit, a magneto-resistive sensing circuit, and an optical sensing circuit.

7. The apparatus of claim 1, wherein the timer circuit generates the signal periodically.

8. A metering circuit comprising:

a sensor circuit coupled to the input to receive a resonant signal corresponding to usage of a resource;

a timer circuit to generate a timer signal at selected intervals; and

a controller coupled to the timer circuit and the sensor circuit, the controller having a first power mode and a second power mode, the first power mode having a lower power consumption than the second power mode, the controller to enter the second power mode and enable the sensor circuit to capture measurements of the resonant signal in response to receiving the timer signal.

9. The metering circuit of claim 8, further including a pulse generator coupled to the controller, the pulse generator to provide an excitation signal to an output in response to a signal from the controller.

10. The metering circuit of claim 9, wherein the controller controls the pulse generator to provide the excitation signal at a first point in time and controls the sensing circuit to wake up at a second point in time.

11. The metering circuit of claim 8, wherein the timer circuit comprises:

a real time clock (RTC) to provide a clock signal; and

an interval timing circuit coupled to the RTC to receive the clock signal and to provide the timer signal at the periodic intervals to the controller.

12. The metering circuit of claim 8, further comprising a state machine circuit coupled to the sensor circuit, the state machine circuit configured to update a first counter and a second counter in response to an output signal from the sensor circuit.

13. The metering circuit of claim 12, further comprising a microcontroller coupled to the first counter and the second counter and responsive to a wakeup signal from the controller to transition from the first power mode to the second power mode.

14. The metering circuit of claim 13, wherein the controller wakes up the microcontroller in response to a peak count exceeding a count threshold.

15. A method of measuring a resonant signal, the method comprising:

selectively providing an excitation signal to an output of a metering circuit at a first point in time;

receiving a resonant signal at an input of the metering circuit in response to the excitation signal; and

providing a wake up signal to a sensing circuit of the metering circuit at a second point in time to transition the sensing circuit from a first power mode to a second power mode for a pre-determined number of clock cycles to count a number of oscillations of the resonant signal, the first power mode having a lower power consumption than the second power mode.

16. The method of claim 15, wherein providing the wake up signal causes the sensing circuit to perform a plurality of measurements of the resonant signal.

17. The method of claim 15, further comprising providing a second wake up signal to a microcontroller unit in response to an event, the microcontroller unit to control at least one input/output (I/O) of the circuit in relation to the second wake up signal.

18. The method of claim 15, further comprising:

receiving a first clock signal from a real time clock; and

determining the first point in time from the first clock signal using an interval timing circuit.

19. The method of claim 15, further comprising selectively enabling a microcontroller in response to a peak count exceeding a count threshold.

20. The method of claim 15, wherein providing the excitation signal at the first point in time comprises providing the excitation signal periodically.