Oscillator based sensor interface circuit

1. An oscillator-based sensor interface circuit arranged for offline error tuning comprising

at least two oscillators, at least one of which is arranged for receiving an electrical signal representative of an electrical quantity, said electrical quantity being a converted physical quantity, and impacting said at least one oscillator's frequency,

phase detection means arranged to compare output signals of said at least two oscillators and for outputting a digital phase detection output signal in accordance with the outcome of said comparing, said phase detector output signal also being an output signal of said oscillator-based sensor interface circuit,

a feedback element arranged for receiving a representation of said digital phase detection output signal and for converting said representation into a feedback signal used directly or indirectly to maintain a given relation between oscillator frequencies of said at least two oscillators,

means for detecting a difference between said at least two oscillators,

at least one tuning element arranged for receiving said detected difference and for tuning at least one characteristic of the oscillator-based sensor interface circuit causing a change in oscillator frequency of at least one of said oscillators to reduce said detected difference.

2. An oscillator-based sensor interface circuit arranged for online error tuning, comprising

at least two oscillators, at least one of which is arranged for receiving an electrical signal representative of an electrical quantity, said electrical quantity being a converted physical quantity and impacting said at least one oscillator's frequency,

chopping circuitry arranged for modulating said electrical signal representative of said electrical quantity with a chopping signal and for feeding said modulated electrical signal to said at least one oscillator,

phase detection means arranged to compare output signals of said at least two oscillators and for outputting a digital phase detection output signal in accordance with the outcome of said comparing, said phase detector output signal also being an output signal of said oscillator-based sensor interface circuit,

whereby said chopping circuitry is further arranged for demodulating said output signals before applying said output signals to said phase detection means or for demodulating said digital phase detection output signal,

said oscillator-based sensor interface circuit further comprising

a feedback element arranged for receiving a representation of said digital phase detection output signal and for converting said representation into a feedback signal used directly or indirectly to maintain a given relation between oscillator frequencies of said at least two oscillators,

detection means for detecting a difference between said at least two oscillators based on said digital phase detection output signal,

at least one tuning element arranged for receiving said detected difference and for tuning at least one characteristic of the oscillator-based sensor interface circuit causing a change in oscillator frequency of at least one of said oscillators to reduce said detected difference.

3. The oscillator-based sensor interface circuit as in claim 2 , further comprising a digital filter arranged for filtering said digital phase detection output signal and for applying said filtered digital phase detection output signal to said feedback element.

4. The oscillator-based sensor interface circuit as in claim 2 , comprising a sensing means arranged for converting said physical quantity comprised in a received signal into said electrical quantity and for outputting said electrical signal representative of said electrical quantity.

5. The oscillator-based sensor interface circuit as in claim 4 , wherein said sensing means comprises a sensor arranged for receiving said signal comprising said physical quantity and a reference element arranged to generate a reference signal.

6. The oscillator-based sensor interface circuit as in claim 4 , comprising a Wheatstone bridge.

7. The oscillator-based sensor interface circuit as in claim 4 , wherein said feedback signal goes back to said sensing means.

8. The oscillator-based sensor interface circuit as in claim 4 , wherein said received signal is one of a pressure, a temperature, a force, a signal from an optical sensing means or from a magnetic sensing means.

9. The oscillator-based sensor interface circuit as in claim 2 , wherein said feedback element comprises at least one current source.

10. The oscillator-based sensor interface circuit as in claim 2 , wherein said phase detection means comprises a flip-flop.

11. The oscillator-based sensor interface circuit as in claim 2 , wherein said means is arranged for detecting said error by making a difference of the digital output signals obtained after said chopping.

12. The oscillator-based sensor interface circuit as in claim 2 , wherein said at least one tuning element arranged for gain tuning at least one of said at least two oscillators.

13. The oscillator-based sensor interface circuit as in claim 2 , wherein said at least one tuning element arranged for offset tuning at least one of said at least two oscillators.