Abstract

We implemented a 48-tap, mixed-signal adaptive FIR filter with 8-bit input and 10-bit output resolution. The filter stores its tap weights in nonvolatile analog memory cells and adapts using the Least-Mean-Square (LMS) algorithm. We run the input through a digital tapped delay line, multiply the digital words with the analog tap weights using mixed-signal multipliers, and adapt the tap coefficients using pulse-based feedback. The accuracy of the weight updates exceeds 13 bits. The total die area is 2.6mm(2) in a 0.35 mum CMOS process. The filter delivers a performance of 19.2GOPS at 200MHz, and consumes 20mW providing a 6mA differential output current.