A refreshable analog VLSI neural network chip with 400 neurons and 40 k synapses

Describes a self-learning neural network chip with refresh on-chip analog synaptic weight storage. The chip integrates 400 neurons and 40000 synapses with 0.8- mu m double poly-Si double metal CMOS technology. Refresh time is less than 300 mu s. The chip retains learned information by repeating refresh at 100 ms intervals. The proposed refresh method is based on the decision made by a subnetwork. The subnetwork learns if the settling states of the main network should be memorized, retains the weights until they are relearned, and stores a 4-b representation of subnetwork weights in a counter. The main network is refreshed according to the output of the subnetwork.<>