Comparison of two thermometer-to-binary decoders for high-performance flash ADCs

The performance of flash analog-to-digital converters is affected significantly by the choice of thermometer-to-binary decoder topology. In this work two different promising decoder topologies, multiplexer-based and ones-counter, are evaluated. Two converters with different decoders, but otherwise similar, are therefore designed. Two test chips are also sent for manufacturing in a 130 nm silicon-on-insulator CMOS technology. The converter performance is evaluated by simulations using foundry provided models. The results show that both decoders can be used in high-speed converters, but the ones-counter decoder is more robust and yield a higher converter efficiency.