US-12625023-B2 - Capacitive MEMS sensing diagnostic mode

Abstract

A pressure sensor includes a microelectromechanical system (MEMS) device having a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device having a first input pad and a second input pad, a measurement interface including a first input and a second input, a first switch coupled between the first input pad and the second input pad, and a second switch coupled between the second input of the measurement interface and the second input pad of the ASIC.

Inventors

• Philipp GREINER
• Elmar Rudolf Bach
• Stefan Gansinger
• Markus Haberler

Assignees

• INFINEON TECHNOLOGIES AG

Dates

Publication Date

20260512

Application Date

20230622

Claims (20)

1. 1 . A pressure sensor comprising: a microelectromechanical system (MEMS) device comprising a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device comprising a first input pad and a second input pad, a measurement interface including a first input and a second input, a first switch coupled between the first input pad and the second input pad, and a second switch coupled between the second input of the measurement interface and the second input pad of the ASIC, wherein the first output pad of the MEMS device is directly connected to the first input pad of the ASIC, and wherein the second output pad of the MEMS device is directly connected to the second input pad of the ASIC.
2. 2 . The pressure sensor of claim 1 , wherein the first pressure sensitive capacitor element and the first reference capacitive element are coupled to a first reference pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the second reference capacitive element are coupled to a second reference pad of the MEMS device.
3. 3 . The pressure sensor of claim 1 , wherein the first pressure sensitive capacitor element and the second reference capacitive element are coupled to the first output pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the first reference capacitive element are coupled to the second output pad of the MEMS device.
4. 4 . The pressure sensor of claim 1 , wherein the measurement interface comprises a differential amplifier.
5. 5 . The pressure sensor of claim 1 , wherein the measurement interface comprises an analog-to-digital converter (ADC).
6. 6 . The pressure sensor of claim 1 , wherein the measurement interface comprises: a first reference voltage source coupled to a first reference pad of the ASIC; and a second reference voltage source coupled to a second reference pad of the ASIC.
7. 7 . A pressure sensor comprising: a microelectromechanical system (MEMS) device comprising a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device comprising a first input pad and a second input pad, a measurement interface comprising a first input and a second input, a first switch coupled between the first input pad of the ASIC and the second input pad of the ASIC, a second switch coupled between the second input of the measurement interface and the second input pad of the ASIC, and a third switch coupled between the first input of the measurement interface and the first input pad of the ASIC, wherein the first output pad of the MEMS device is directly connected to the first input pad of the ASIC, and wherein the second output pad of the MEMS device is directly connected to the second input pad of the ASIC.
8. 8 . The pressure sensor of claim 7 , wherein the first pressure sensitive capacitor element and the first reference capacitive element are coupled to a first reference pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the second reference capacitive element are coupled to a second reference pad of the MEMS device.
9. 9 . The pressure sensor of claim 7 , wherein the first pressure sensitive capacitor element and the second reference capacitive element are coupled to the first output pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the first reference capacitive element are coupled to the second output pad of the MEMS device.
10. 10 . The pressure sensor of claim 7 , wherein the measurement interface comprises a differential amplifier.
11. 11 . The pressure sensor of claim 7 , wherein the measurement interface comprises an analog-to-digital converter (ADC).
12. 12 . The pressure sensor of claim 7 , wherein the measurement interface comprises: a first reference voltage source coupled to a first reference pad of the ASIC; and a second reference voltage coupled to a second reference pad of the ASIC.
13. 13 . A pressure sensor comprising: a microelectromechanical system (MEMS) device comprising a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device comprising a first input pad and a second input pad, a measurement interface comprising a first input and a second input, a first switch coupled between the second input pad of the ASIC and a source of bias voltage, a second switch coupled between the second input pad of the ASIC and the second input of the measurement interface, a third switch coupled between the first input pad of the ASIC and the source of bias voltage, and a fourth switch coupled between the first input pad of the ASIC and the first input of the measurement interface, wherein the first output pad of the MEMS device is directly connected to the first input pad of the ASIC, and wherein the second output pad of the MEMS device is directly connected to the second input pad of the ASIC.
14. 14 . The pressure sensor of claim 13 , further comprising a fifth switch coupled between the first input pad of the ASIC and the second input pad of the ASIC.
15. 15 . The pressure sensor of claim 13 , wherein the first pressure sensitive capacitor element and the first reference capacitive element are coupled to a first reference pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the second reference capacitive element are coupled to a second reference pad of the MEMS device.
16. 16 . The pressure sensor of claim 13 , wherein the first pressure sensitive capacitor element and the second reference capacitive element are coupled to the first output pad of the MEMS device, and wherein the second pressure sensitive capacitor element and the first reference capacitive element are coupled to the second output pad of the MEMS device.
17. 17 . The pressure sensor of claim 13 , wherein the measurement interface comprises a differential amplifier.
18. 18 . The pressure sensor of claim 13 , wherein the measurement interface comprises an analog-to-digital converter (ADC).
19. 19 . The pressure sensor of claim 13 , wherein the measurement interface comprises: a first reference voltage source coupled to a first reference pad of the ASIC; and a second reference voltage source coupled to a second reference pad of the ASIC.
20. 20 . The pressure sensor of claim 13 , wherein the first switch, the second switch, the third switch, and the fourth switch are set in a first configuration for a normal mode of operation, and wherein the first switch, the second switch, the third switch, and the fourth switch are set in a second configuration for a diagnostic mode of operation.

Description

TECHNICAL FIELD The present invention relates generally to a capacitive microelectromechanical system (MEMS) sensing diagnostic mode. BACKGROUND A capacitive pressure sensor can be implemented using pressure sensitive capacitor elements and reference capacitor elements in a fully differential bridge configuration. This configuration measures the absolute pressure expressed as a differential signal. Furthermore, by reconfiguring the bridge, a diagnostic measurement can also be performed. The diagnostic mode measures the balance (matching) between the bridge elements while the excitation effect of the measurement unit (e.g. air pressure) is strongly suppressed. An unbalanced bridge can be evidence of a defect (e.g. due to particle contamination) and can thus be used to screen out such devices. Furthermore, diagnostic measurements allow continuous monitoring of the MEMS over the device lifetime. FIG. 1 depicts a capacitive pressure sensor bridge 100A configured in normal operation and a capacitive pressure sensor bridge 100B configured in diagnosis mode, but both using a differential read out according to the prior art. Capacitive pressure sensor bridge 100A comprises reference capacitors elements C1 and C4, and pressure sensitive capacitors elements C2 and C3. Reference capacitor element C1 is coupled between terminal 102 designated VREF_P and terminal 104 designated VOUT_N, and reference capacitor element C4 is coupled between terminal 108 designated VREF_N and terminal 106 designated VOUT_P. Pressure sensitive capacitor element C2 is coupled between terminal 102 designated VREF_P and terminal 106 designated VOUT_P, and pressure sensitive capacitor element C3 is coupled between terminal 108 designated VREF_N and terminal 104 designated VOUT_N. The differential voltage between terminal 104 and terminal 106 provides a differential voltage representative of an input pressure, such as ambient air pressure. Capacitive pressure sensor bridge 100B comprises reference capacitors elements C1 and C4, and pressure sensitive capacitors elements C2 and C3. Reference capacitor element C1 is coupled between terminal 102 designated VREF_P and terminal 104 designated VOUT_N, and reference capacitor element C4 is coupled between terminal 102 designated VOUT_N and terminal 106 designated VOUT_P. Pressure sensitive capacitor element C2 is coupled between terminal 108 designated VREF_N and terminal 106 designated VOUT_P, and pressure sensitive capacitor element C3 is coupled between terminal 108 designated VREF_N and terminal 104 designated VOUT_N. The differential voltage between terminal 104 and terminal 106 provides a differential voltage representative of an imbalance between a given capacitive element, and the matched values of the other three capacitive elements. While capacitive pressure sensor bridge 100A is configured for normal operation and capacitive pressure sensor bridge 100B is configured for the diagnosis mode, it is evident that additional switches are needed to reconfigure capacitive pressure sensor bridge 100A to assume the configuration of capacitive pressure sensor bridge 100B. In MEMS technology, however, there are typically no CMOS devices for switches available. Additional switches must therefore be incorporated on to a corresponding application-specific integrated circuit (ASIC) in communication with the MEMS device. Consequently, additional connections (bonding pads, and bond wires) between the MEMS device and the ASIC are needed. SUMMARY According to an embodiment, a pressure sensor comprises a microelectromechanical system (MEMS) device comprising a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device comprising a first input pad and a second input pad, a measurement interface including a first input and a second input, a first switch coupled between the first input and the second input, and a second switch coupled between the second input of the measurement interface and the second input pad of the ASIC. According to another embodiment, a pressure sensor comprises a microelectromechanical system (MEMS) device comprising a first pressure sensitive capacitor element, a second pressure sensitive capacitor element, a first reference capacitive element, and a second reference capacitive element arranged in a bridge configuration, a first output pad, and a second output pad; and an application-specific integrated circuit (ASIC) in electrical communication with the MEMS device comprising a first input pad and a second input pad, a measurement interface comprising a first input and a second input, a first switch coupled between the first input of the measurement interface and the second input of the measurement