MEMS airflow sensor die incorporating additional circuitry on the die

• US 8,640,552 B2
• Filed: 09/06/2011
• Issued: 02/04/2014
• Est. Priority Date: 09/06/2011
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Qasimi, Mohammed Abdul Javvad, Ricks, Lamar Floyd
• Primary Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US13/226,264
• Publication Number:
  US 20130055826A1
• Time in Patent Office: 882 Days
• Field of Search: 738/610.2, 738/610.5, 732/042.3, 732/042.6
• US Class Current: 73/861.02
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/692 Thin-film arrangements
• CPC Class Codes: G01F 1/698 Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
• CPC Class Codes: G01F 15/02 Compensating or correcting for variations in pressure, density or temperature

Abstract

A MEMS airflow sensor die having a heater control circuit, differential instrumentation amplifier, temperature compensation, and/or offset correction circuitry integrated with an airflow sensor on the MEMS die. The added circuitry may be placed on space available on the basic airflow die with MEMS fabrication techniques without enlarging the sensor die. The die with the added circuitry may result in a device having a reduced form factor, improved reliability and lower cost.

Claims

1. A fluid flow sensor arrangement comprising:

a micro electromechanical systems fabricated fluid flow sensor die having a fluid flow sensor;

a temperature sensor formed in available space on the die; and

a temperature compensation circuit formed in available space on the die and connected to the temperature sensor and to an output of the fluid flow sensor; and

wherein;

the output of the fluid flow sensor indicates a magnitude of a flow of fluid through the flow sensor; and

changes of the magnitude of the flow of fluid indicated at output of the flow sensor due to a temperature of the die are compensated with the temperature compensation circuit.

2. The arrangement of claim 1, further comprising:

an amplifier formed in available space on the die to amplify the output of the flow sensor; and

wherein the amplifier comprises a differential circuit to reduce offsets at the output.

3. The arrangement of claim 1, further comprising:

a heating element on the die; and

a heater control circuit formed on the die and connected to the temperature sensor and the heating element to maintain a pre-selected operating temperature for the fluid flow sensor.

4. The arrangement of claim 3, wherein:

the fluid flow sensor is an airflow sensor; and

the temperature sensor, temperature compensation circuit, the amplifier, the heating element and the heater control circuit are formed on the die with micro electromechanical systems fabrication techniques.

5. The arrangement of claim 4, wherein:

the flow sensor comprises a bridge based moisture resistant micro electromechanical systems structure; and

the structure comprises at least a partial Wheatstone configuration.

6. The arrangement of claim 4, wherein the flow sensor comprises a membrane based moisture resistant micro electromechanical systems structure.

7. A fluid flow sensor die comprising:

a given micro electromechanical systems fabricated fluid flow sensor die having a flow sensor; and

an amplifier added to the flow sensor die; and

wherein;

the amplifier is formed on the flow sensor die with micro electromechanical systems fabrication techniques; and

the amplifier is connected to an output of the flow sensor.

8. The die of claim 7, further comprising:

flow sensor output offset correction circuitry added to and formed on the flow sensor die with micro electromechanical systems fabrication techniques; and

wherein the flow sensor output offset correction circuitry is interconnected with the amplifier.

9. The die of claim 7, wherein:

the flow sensor comprises a Wheatstone bridge; and

the amplifier comprises a differential circuit.

10. The die of claim 9, further comprising a heater control circuit added with micro electromechanical systems fabrication techniques to the flow sensor die.

11. The die of claim 10, further comprising a temperature compensation circuit added with micro electromechanical systems fabrication techniques to the flow sensor die.

12. The die of claim 7, wherein:

the die comprises silicon; and

the flow sensor is selected from a group consisting of a bridge based moisture resistant airflow sensor and a membrane based moisture resistant airflow sensor.

13. A fluid flow sensor system comprising:

a micro electromechanical systems fabricated flow sensor die having a fluid flow sensor; and

a heater control circuit formed on the flow sensor die with micro electromechanical systems fabrication techniques.

14. The system of claim 13, further comprising:

a differential amplifier formed in the micro electromechanical systems fabricated flow sensor die; and

wherein the differential amplifier is connected to an output of the flow sensor.

15. The system of claim 14, further comprising:

a temperature compensation circuit formed in the micro electromechanical systems fabricated flow sensor die; and

wherein the temperature compensation circuit compensates for variations of magnitude indications of flow from the output of the flow sensor due to temperature changes in the flow sensor die.

16. The system of claim 15, wherein the flow sensor is a bridge-based micro electromechanical systems flow die.

17. The system of claim 15, wherein the flow sensor is a membrane-based micro electromechanical systems flow die.

18. The system of claim 15, wherein the flow sensor comprises a Wheatstone bridge.

19. The system of claim 13, further comprising:

an amplifier connected to an output of the fluid flow sensor;

a die temperature sensor;

a temperature compensation circuit connected to the die temperature sensor and to an output of the amplifier; and

a die heating element; and

wherein;

the heater control circuit is connected to the die temperature sensor and the die heating element; and

the amplifier, the die temperature sensor, the temperature compensation circuit, the die heating element, and the heater control circuit are formed in available space on the flow sensor die with micro electromechanical systems fabrication techniques.

20. The system of claim 19, wherein the fluid flow sensor is an airflow sensor.