TECHNICAL FIELD

The present disclosure relates generally to an electronic system and method, and, in particular embodiments, to a routing for direct time-of-flight (DTOF) sensors.

BACKGROUND

DTOF image sensors use time-of-flight (ToF) techniques to determine distance towards a target to provide, e.g.,3D-depth maps.FIG. 1shows a schematic diagram of DTOF system100. DTOF system100includes illumination source106, single photon avalanche diode (SPAD) array104, time to digital converters (TDCs)102, and processor11o. Routing block112couple SPAD array104to TDCs102(e.g., via metal traces and logic circuits). SPAD array104, routing block112and TDCs102are generally implemented in the same integrated circuit (IC).

A DTOF sensor generally includes an image capture mechanism, data converter(s), frequency and timing generation circuits, and at least a portion of digital signal processing and data compression/storage. Therefore, in some cases, TDCs102, SPAD array104, timing generator circuit108, and routing block112are jointly referred to as a DTOF sensor. In some cases, the DTOF sensor also includes processor110(or a portion of processor110).

During normal operation, illumination source106emits light pulses112towards object116, e.g., at times controlled by timing generator circuit108. Reflected light pulses114are sensed by SPAD array104and routed to TDCs102(which are outside SPAD array104). TDCs102generate digital representations of the time between the emissions of light pulses112and receptions of reflected light pulses114. Processor110then determines the distance to object116, e.g., by generating ToF histograms in a known manner based on the outputs of TDCs102.

SPAD array104may be formed by a plurality of pixels arranged in rows and columns, where each pixel includes one or more SPADs. For each pixel, a conventional DTOF signal chain is shown inFIG. 2. As shown inFIG. 2, SPADs202(of SPAD array104) are coupled to TDC206(of TDCs102) via routing block204(where routing block204may optionally include an OR tree). Even though SPADs202includes 8 SPADs, a different number of SPADs, such as 1, 2, 4, 10, 16, or other may also be used.

SUMMARY

In accordance with an embodiment, a time-of-flight (ToF) sensor includes: an array of pixels arranged in rows and columns, the array of pixels including first and second subsets of pixels, each pixel of the array of pixels configured to generate event signals; a first plurality of time to digital converters (TDCs); a second plurality of TDCs; a first routing bus coupled to the first and second pluralities of TDCs and to the first and second subsets of pixels, the first routing bus including a first plurality of bus drivers associated with the first subset of pixels and a second plurality of bus drivers associated with the second subset of pixels, the first plurality of bus drivers coupled to the second plurality of TDCs via the second plurality of bus drivers, and the second plurality of bus drivers coupled to the first plurality of TDCs via the first plurality of bus drivers; and a controller configured to: when the first subset of pixels is active and the second subset of pixels is not active, control the first plurality of bus drivers to route event signals from half of the pixels of the first subset of pixels to the first plurality of TDCs and control the first and second plurality of bus drivers to route event signals from the other half of the pixels of the first subset of pixels to the second plurality of TDCs, and when the first subset of pixels is not active and the second subset of pixels is active, control the first plurality of bus drivers to route event signals from the second subset of pixels to the first plurality of TDCs.

In accordance with an embodiment, a method includes: activating a first subset of pixels of an array of pixels of a time-of-flight (ToF) sensor, the array of pixels being arranged in rows and columns; when the first subset of pixels is active, controlling a first plurality of bus drivers of a first routing bus to route event signals from half of the pixels of the first subset of pixels to a first plurality of TDCs and controlling the first plurality of bus drivers and a second plurality of bus drivers to route event signals from the other half of the pixels of the first subset of pixels to a second plurality of TDCs, where the first plurality of bus drivers is coupled to the second plurality of TDCs via the second plurality of bus drivers, where the second plurality of bus drivers is coupled to the first plurality of TDCs via the first plurality of bus drivers, where the first plurality of bus drivers is associated with the first subset of pixels, and where the second plurality of bus drivers associated with a second subset of pixels of the array of pixels; activating the second subset of pixels; and when the second subset of pixels is active, controlling the first plurality of bus drivers to route event signals from the second subset of pixels to the first plurality of TDCs.

In accordance with an embodiment, an integrated circuit (IC) includes: an array of pixels arranged in rows and columns, the array of pixels including a first subset of pixels, each pixel of the array of pixels configured to generate event signals; a top plurality of time to digital converters (TDCs) physically disposed at the top of the array of pixels; a bottom plurality of TDCs physically disposed at the bottom of the array of pixels; a routing bus coupled to the top and bottom pluralities of TDCs and to the first subset of pixels, the routing bus including a plurality of bus drivers associated with the first subset of pixels; and a controller configured to: when the first subset of pixels is active, control the plurality of bus drivers to route event signals from a top half of the pixels of the first subset of pixels to the top plurality of TDCs and to route event signals from a bottom half of the pixels of the first subset of pixels to the bottom plurality of TDCs, and when the first subset of pixels is not active, control all of the plurality of bus drivers to route event signals of the routing bus to the top plurality of TDCs.

In accordance with an embodiment, a time-of-flight (ToF) sensor includes: an array of pixels arranged in rows and columns, each pixel of the array of pixels configured to generate event signals, the array of pixels including a subset of pixels; a routing bus coupled to the subset of pixels; a plurality of time-capture circuits coupled to the routing bus; and a controller configured to: when the subset of pixels is in integration mode, route event signals from a first pixel of the subset of pixels to a first time-capture circuit of the plurality of time-capture circuits via a first routing line of the routing bus, and when the subset of pixels is in readout mode, route data from the first time-capture circuit to a reading circuit via the first routing line.

In accordance with an embodiment, a method includes: setting a subset of pixels of an array of pixels of a time-of-flight (ToF) sensor to integration mode, the array of pixels being arranged in rows and columns; when the subset of pixels is in integration mode, routing event signals from a first pixel of the subset of pixels to a first time-capture circuit of a plurality of time-capture circuits via a first routing line of a routing bus; setting the subset of pixels to readout mode; and when the subset of pixels is in readout mode, routing data from the first time-capture circuit to a reading circuit via the first routing line.

In accordance with an embodiment, an integrated circuit (IC) includes: an array of pixels arranged in rows and columns, each pixel of the array of pixels configured to generate event signals, the array of pixels including a subset of pixels; a routing bus coupled to the subset of pixels, the routing bus including J routing lines, where J is a positive integer greater than 1, where each routing line of the J routing lines is coupled to more than 1 pixels of the subset of pixels; a plurality of time-capture circuits coupled to the routing bus; and a controller configured to: when the subset of pixels is in integration mode, route event signals from a first pixel of the subset of pixels to a first time-capture circuit of the plurality of time-capture circuits via a first routing line of the routing bus, and when the subset of pixels is in readout mode, route data from the first time-capture circuit to a reading circuit via the first routing line.

