A Compact 140nW/input Winner-Take-All Circuit for Spiking Neural Networks

Solving classification problems using Spiking Neural Networks (SNNs) involves determining the most active neuron in the output layer. Scalable, low-power and low-area hardware solutions for such decision-making are vital for neuromorphic edge applications to meet power and space constraints. In this work, we propose a low-power, compact Winner-Take-All (WTA) circuit, a multi-input multi-output dynamic threshold comparator that simultaneously compares multiple analog voltage inputs and provides a one-hot-encoded digital output vector indicating the result of the classification. The design eliminates the need for cascading and a dedicated feedback circuit. A spike integrator stage captures the temporal activity of a set of neurons, and these activities are compared and digitized by the proposed WTA comparator stage. The proposed WTA designed in GF45RFSOI technology, exhibits self-excitation and global-inhibition properties, offers scalability, consumes 44% less power (140 nW ) and occupies a 40% lower area (166 μm
²
), compared to state-of-the-art.