Signal conditioning methods and circuits for a capacitive sensing integrated tire pressure sensor
US7454967B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jul 9, 2007 |
| Grant date | Nov 25, 2008 |
| Priority date | — |
| Expiry date | Jul 9, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01L9/12
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A tire pressure monitoring system is provided that includes a switched capacitor circuit having a clock with two non-overlapping clock phases that control a state of analog switches of the switched capacitor circuit. The system uses tire pressure sensor MEMS capacitors that are measured differentially. A capacitance-to-voltage converter is connected to the MEMS sense capacitor, and a sigma-delta converter having a comparator with a first digital output state and a second digital output state is used. The first output state is a sum of reference voltages and the second output state is a difference of the reference voltages. An average value of the capacitance-to-voltage converter output is driven to a zero value and a digital output is provided of the average output states that is equal to a difference between the MEMS capacitors divided by their sum multiplied by a ratio of the reference voltages.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.