MEMS Capacitive Pressure Sensor Diagnostic Bridge Reconfiguration
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Solution Overview
Problem
Existing capacitive pressure sensors in MEMS technology require additional switches and connections (bonding pads and bond wires) to reconfigure between normal and diagnostic modes, which are not available in CMOS devices, leading to inefficiencies and increased complexity.
Innovation Solution
Implementing a diagnostic mode in MEMS devices that short the differential outputs within the device for single-ended (common mode) measurement, eliminating the need for additional connections to the ASIC, and using switches on the ASIC to combine signals into a single-ended configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional switches are incorporated on the ASIC to enable diagnostic mode, then the bridge can be reconfigured for diagnostic measurements, but the device complexity increases and additional bonding pads and bond wires are needed
Solution Approach 1:
The patent merges the diagnostic mode functionality with the existing normal operation mode by using the same differential output pads. The ASIC switches between measuring differential signals (normal mode) and single-ended signals (diagnostic mode) using the same physical connections, eliminating the need for separate bonding pads for diagnostic mode.
Solution Approach 2:
The differential output pads serve dual purposes: they function as differential outputs during normal pressure measurement operations and as single-ended outputs during diagnostic mode. This multi-functionality allows the same hardware to perform both measurement and diagnostic tasks without additional connections.
2Adaptability or versatility
If additional bonding pads and bond wires are added between MEMS device and ASIC, then diagnostic mode can be implemented, but the manufacturing complexity and potential for connection failures increase
Solution Approach 1:
The patent combines the diagnostic mode signal path with the existing differential output signal path. By using the same bonding pads and bond wires for both normal and diagnostic modes through software-controlled switching on the ASIC side, the manufacturing process remains simple without requiring additional bonding operations.
3Measurement precision
If a fully differential bridge configuration is used for normal operation, then absolute pressure can be measured accurately, but diagnostic measurements require additional reconfiguration switches
Solution Approach 1:
The patent replaces physical mechanical switches with software-controlled digital switches on the ASIC. The differential to single-ended conversion is achieved through digital signal processing and switching controlled by a microcontroller, eliminating the need for additional physical switches in the MEMS device itself.
Data Source
AI summary
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.