Analog VLSI long-term dynamic storage

We present a scalable and modular VLSI architecture for long-term, large-scale dynamic analog storage. The analog values are quantized locally and refreshed autonomously on a 2-D memory bank of capacitors, with direct read/write access in both digital and analog formats. Quantization is performed on-chip in a multiplexed arrangement, using a linear bank of bi-directional bit-serial A/D/A (analog-to-digital and digital-to-analog) converters. The technique of partial incremental refresh is used to assure long-term memory retention in the presence of noise and quantization errors. Results are included on a fabricated CMOS chip with 128 memory cells and with integrated A/D/A quantizers, demonstrating stable memory operation at 8-bit effective analog resolution over a time interval exceeding 10/sup 9/ refresh cycles (several days).