Oscillator arrangement for time-to-digital converter for large array of time-of-flight image sensor devices
An oscillator arrangement for time-to-digital converters for a 3D image sensor device includes a plurality of oscillators arranged as an array each oscillator being associated to one time-to-digital converter, and at least one coupling unit respectively arranged between at least two of the oscillators, so that oscillation in the at least two oscillators at a fundamental frequency is synchronized between the at least two coupled oscillators.
1. An oscillator arrangement for time-to-digital converters for a 3D image sensor device, comprising:
a plurality of oscillators arranged as an array each oscillator being associated to one time-to-digital converter;
at least one coupling unit respectively arranged between at least two of the oscillators, so that oscillation in the at least two oscillators at a fundamental frequency is synchronized between the at least two coupled oscillators.
2. The oscillator arrangement according to claim 1 , wherein the at least one coupling unit are respectively arranged between two neighboring oscillators of the array.
3. The oscillator arrangement according to claim 2 , wherein each two neighboring oscillators of the array are coupled with at least one coupling unit.
4. The oscillator arrangement according to claim 1 , wherein the at least one coupling unit includes an impedance.
5. The oscillator arrangement according to claim 4 , wherein the coupling unit comprise one or more coupling resistors and/or one or more coupling capacitors and/or one or more coupling inductances.
6. The oscillator arrangement according to claim 1 , wherein the plurality of oscillators comprise a plurality of relaxation oscillators, LC-tank oscillators or micromechanical oscillators.
7. The oscillator arrangement according to claim 1 , wherein the oscillators are formed as ring oscillators each comprising a number of inverters coupled with output to input interconnects in a closed loop, wherein each coupling unit connects one output to input interconnect of one ring oscillator to another output to input interconnect of another ring oscillator.
8. The oscillator arrangement according to claim 7 , wherein one output to input interconnect of the ring oscillator is coupled to a counter wherein the output to input interconnect of one ring oscillator and the output to input interconnects of another one of the ring oscillators which are coupled via the coupling unit, have the same distance of the output to input interconnects coupled to the counter in terms of inverters.
9. The oscillator arrangement according to claim 1 , wherein a PLL circuit is provided which controls the oscillators depending on a reference frequency signal to adjust the frequency to a provided reference frequency, wherein particularly the PLL circuit is configured by providing a common control voltage depending on one of the oscillator phases with respect to the reference frequency to control all oscillators.
10. A 3D image sensor device comprising:
a photodiode array providing a plurality of pixels;
the oscillator arrangement according to claim 1 , and
time-to-digital converters each associated to one of the oscillators of the oscillator arrangement so that the respective oscillator provides a timing information to the respective time to digital converter.