CIRCUIT AND METHOD FOR CONTROLLING A SPAD ARRAY

• US 20160284743A1
• Filed: 10/29/2015
• Published: 09/29/2016
• Est. Priority Date: 03/23/2015
• Status: Active Grant

• Current Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Grenoble 2 SAS (STMicroelectronics NV), Stmicroelectronics (Research & Development) Limited (STMicroelectronics NV)
• Inventors: MELLOT, Pascal, MCLEOD, Stuart, RAE, Bruce, DRADER, Marc
• Granted Patent: US 9,786,701 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/4865 Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak peak detection in noise, signal conditioning G01S7/487
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: H01L 27/1443 with at least one potential jump or surface barrier
• CPC Class Codes: H01L 27/1446 in a repetitive configuration
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14818 Optical shielding
• CPC Class Codes: H01L 31/02164 for shielding light, e.g. light blocking layers, cold shields for infrared detectors
• CPC Class Codes: H01L 31/107 the potential barrier working in avalanche mode, e.g. avalanche photodiodes
• CPC Class Codes: H04N 25/773 comprising photon counting circuits, e.g. single photon detection [SPD] or single photon avalanche diodes [SPAD]

Abstract

A circuit may include an array of single photon avalanche diode (SPAD) cells, each SPAD cell configured to be selectively enabled by an activation signal. The circuit may include a control circuit configured to selectively enable a subset of the array of SPAD cells based on a measured count rate of the array of SPAD cells.

Claims

1-14. -14. (canceled)

15. A circuit comprising:

an array of single photon avalanche diode (SPAD) cells, each SPAD cell configured to be selectively enabled by an activation signal; and

a control circuit configured to selectively enable a subset of said array of SPAD cells based on a measured count rate of said array of SPAD cells.

16. The circuit of claim 15 wherein at least one SPAD cell of said array of SPAD cells comprises a shield, and a photosensitive zone at least partially shielded by said shield such that the at least one SPAD cell has a lower sensitivity than other SPAD cells of said array of SPAD cells.

17. The circuit of claim 16 wherein said shield defines an opening having an area between 5% and 90% of said photosensitive zone.

18. The circuit of claim 16 wherein the enabled subset of said array of SPAD cells comprises the at least one SPAD cell.

19. The circuit of claim 15 wherein the measured count rate comprises a greatest of a plurality of measured count rates.

20. The circuit of claim 15 further comprising a light source;

and wherein said control circuit comprises an adder configured to generate the measured count rate by adding an ambient rate measured while said light source is disabled to a rate measured while said light source is enabled.

21. The circuit of claim 16 wherein said control circuit is configured to determine, based on the measured count rate, a first value indicating a number of SPAD cells of said array of SPAD cells to form the enabled subset of said array of SPAD cells.

22. The circuit of claim 21 wherein said control circuit is configured to compare the first value with a threshold value and to selectively enable the at least one SPAD cell of the array of SPAD cells based upon the comparison.

23. The circuit of claim 15 further comprising a count circuit configured to count events detected by each enabled SPAD cell of the array of SPAD cells during a count window.

24. The circuit of claim 22 wherein said array of SPAD cells is disabled during a deadtime period between detection phases;

and wherein said control circuit is configured to generate the threshold value based upon the deadtime period.

25. The circuit of claim 15 wherein the array of SPAD cells comprises first, second and third subsets of SPAD cells;

and wherein said control circuit is configured to generate a first enable signal for selectively enabling the first subset, and a second enable signal for selectively enabling the second subset.

26. The circuit of claim 15 wherein each SPAD cell comprises a first transistor having first and second conducting nodes coupled between an output node and a first supply voltage rail, and a control node configured to be controlled based upon the activation signal.

27. The circuit of claim 15 wherein each SPAD cell comprises:

an avalanche diode; and

a second transistor having first and second conducting nodes coupled between said avalanche diode and a second supply voltage rail, and a control node configured to be controlled based on the activation signal.

28. A circuit comprising:

an array of single photon avalanche diode (SPAD) cells, each SPAD cell configured to be selectively enabled by an activation signal;

a control circuit configured to selectively enable a subset of said array of SPAD cells based on a measured count rate of said array of SPAD cells;

at least one SPAD cell of said array of SPAD cells comprising a shield, and a photosensitive zone at least partially shielded by said shield such that the at least one SPAD cell has a lower sensitivity than other SPAD cells of said array of SPAD cells; and

a light source coupled to said control circuit;

said control circuit comprising an adder configured to generate the measured count rate by adding an ambient rate measured while said light source is disabled to a rate measured while said light source is enabled.

29. The circuit of claim 28 wherein said shield defines an opening having an area between 5% and 90% of said photosensitive zone.

30. The circuit of claim 28 wherein the enabled subset of said array of SPAD cells comprises the at least one SPAD cell.

31. The circuit of claim 28 wherein the measured count rate comprises a greatest of a plurality of measured count rates.

32. The circuit of claim 28 wherein said control circuit is configured to determine, based on the measured count rate, a first value indicating a number of SPAD cells of said array of SPAD cells to form the enabled subset of said array of SPAD cells.

33. A method for operating a circuit comprising an array of single photon avalanche diode (SPAD) cells, each SPAD cell configured to be selectively enabled by an activation signal, the method comprising:

operating a control circuit to selectively enable a subset of the array of SPAD cells based on a measured count rate of the array of SPAD cells.

34. The method of claim 33 wherein at least one SPAD cell of the array of SPAD cells comprises a shield, and a photosensitive zone at least partially shielded by the shield such that the at least one SPAD cell has a lower sensitivity than other SPAD cells of the array of SPAD cells.

35. The method of claim 34 wherein the shield defines an opening having an area between 5% and 90% of the photosensitive zone.

36. The method of claim 34 wherein the enabled subset of the array of SPAD cells comprises the at least one SPAD cell.

37. The method of claim 33 wherein the measured count rate comprises a greatest of a plurality of measured count rates.

38. The method of claim 33 further comprising operating the control circuit to generate the measured count rate by adding an ambient rate measured while the light source is disabled to a rate measured while the light source is enabled.