Adaptive priority toggle asynchronous tree arbiter for AER-based image sensor

In this paper, we reported an adaptive priority toggle asynchronous tree arbiter for Address Event Representation (AER)-based image sensors. Simultaneous requests from event-triggered pixels, event latency, timing error and jitter are the inherent issues in AER-based read-out circuits. Fixed priority arbiter often results in unfair allocation of bus resource to only “privileged” pixels thus resulting in timing error. The proposed arbiter is able to reduce the timing error by toggling the requests priority during simultaneous requests. This also achieves the fair allocation of bus resource to all pixels. The featured eager propagation scheme allows the requests to propagate towards higher hierarchy in the tree during the arbitration process. As a result, latency and jitter problems can be reduced. Simulation result reveals that single event delay for 128-way tree arbiter is 4.2 ns and therefore, for 128 × 128 array, such arbiter can process up to 238.09M event/s which is more than 15 times faster than the speed of the reported AER sensor. The arbiter layout was realized with 2P4M 0.35μm CMOS process with a silicon area of 78 × 18μm² and had been implemented in 80 × 80 array AER temporal contrast sensor.