Temperature-compensated timing signal generator

• US 10,852,199 B1
• Filed: 11/29/2018
• Issued: 12/01/2020
• Est. Priority Date: 09/09/2011
• Status: Active Grant

• Current Assignee: SiTime Corporation (Megachips Corporation)
• Original Assignee: SiTime Corporation (Megachips Corporation)
• Inventors: Perrott, Michael H., Lee, Shungneng
• Primary Examiner(s): Gannon, Levi
• Application Number:
  US16/205,107
• Time in Patent Office: 733 Days
• Field of Search: 331154, 331176
• CPC Class Codes: G01K 2219/00 Thermometers with dedicated analog to digital converters
• CPC Class Codes: G01K 7/12 Arrangements with respect to the cold junction, e.g. preventing influence of temperature of surrounding air
• CPC Class Codes: G01K 7/16 using resistive elements resistive elements per se H01C, H01L
• CPC Class Codes: G01K 7/186 using microstructures
• CPC Class Codes: G01K 7/22 the element being a non-linear resistance, e.g. thermistor G01K7/26 takes precedence
• CPC Class Codes: G01K 7/226 using microstructures, e.g. silicon spreading resistance
• CPC Class Codes: G01K 7/34 using capacitative elements capacitors per se H01G
• CPC Class Codes: H03B 5/04 Modifications of generator to compensate for variations in physical values, e.g. power supply, load, temperature
• CPC Class Codes: H03B 5/30 with frequency-determining element being electromechanical resonator
• CPC Class Codes: H03H 9/02244 of microelectro-mechanical resonators
• CPC Class Codes: H03L 1/02 against variations of temperature only

Abstract

The temperature-dependent resistance of a MEMS structure is compared with an effective resistance of a switched CMOS capacitive element to implement a high performance temperature sensor.

Claims

1. A pulse train generator comprising:

a first element having a resistance that varies with temperature;

a microelectromechanical (MEMS) oscillator to generate a pulse train having an effective frequency dependent on a control value;

a switched component network that exhibits an effective resistance according to the effective frequency of the pulse train; and

control circuitry to iteratively adjust the control value based on a time-varying difference between the resistance of the first element and the effective resistance of the switched component network.

2. The pulse train generator of claim 1 wherein the switched component network comprises a plurality of capacitive elements and a plurality of resistive elements interconnected via a plurality of switch elements.

3. The pulse train generator of claim 1 wherein the control circuitry to iteratively adjust the control value comprises circuitry to adjust the control value such that the MEMS oscillator adjusts the effective frequency of the pulse train in a direction that increases or decreases the effective resistance of the switched component network to reduce the time-varying difference between the resistance of the first element and the effective resistance of the switched component network.

4. The pulse train generator of claim 1 wherein the control circuitry to iteratively adjust the control value comprises circuitry to increment or decrement a digital instance of the control value.

5. The pulse train generator of claim 1 wherein the first element comprises a MEMS resistor.

6. The pulse train generator of claim 1 wherein the switched component network generates a frequency-dependent DC voltage corresponding to the effective resistance of the switched component network.

7. The pulse train generator of claim 6 wherein the switched component network generates the frequency-dependent DC voltage across one or more switched capacitive elements thereof.

8. The pulse train generator of claim 6 wherein the switched component network generates the frequency-dependent DC voltage across one or more switched resistor elements thereof.

9. The pulse train generator of claim 1 wherein the MEMS oscillator and first element are thermally coupled.

10. The pulse train generator of claim 1 wherein the MEMS oscillator comprises a MEMS resonator.

11. A method of operation within a pulse train generator, the method comprising:

generating, within a microelectromechanical (MEMS) oscillator, a pulse train having an effective frequency according to a control value;

generating an effective resistance within a switched component network according to the effective frequency of the pulse train; and

iteratively adjusting the control value based on a time-varying difference between a temperature-dependent resistance of a first element and the effective resistance of the switched component network.

12. The method of claim 11 wherein iteratively adjusting the control value comprises adjusting the effective frequency of the pulse train in a direction that increases or decreases the effective resistance of the switched component network to reduce the time-varying difference between the temperature-dependent resistance of the first element and the effective resistance of the switched component network.

13. The method of claim 11 wherein iteratively adjusting the control value comprises incrementing or decrementing a digital instance of the control value.

14. The method of claim 11 wherein the first element comprises a MEMS resistor.

15. The method of claim 11 wherein generating an effective resistance within a switched component network according to the effective frequency of the pulse train comprises generating a frequency-dependent DC voltage corresponding to the effective resistance of the switched component network.

16. The method of claim 15 wherein generating the frequency-dependent DC voltage comprises generating the frequency-dependent DC voltage across one or more switched capacitive elements within the switched component network.

17. The method of claim 15 wherein generating the frequency-dependent DC voltage comprises generating the frequency-dependent DC voltage across one or more switched resistor elements within the switched component network.

18. The method of claim 11 wherein the MEMS oscillator and first element are thermally coupled.

19. The method of claim 11 wherein generating the periodic timing signal within the MEMS oscillator comprises generating the periodic timing signal within a MEMS oscillator having a MEMS resonator.

20. A pulse train generator comprising:

a first element having a resistance that varies with temperature;

a microelectromechanical (MEMS) oscillator to generate a pulse train having an effective frequency dependent on a control value;

means for generating an effective resistance according to the effective frequency of the pulse train; and

means for iteratively adjusting the control value based on a time-varying difference between the effective resistance and the resistance of the first element.