A 6-bit Segmented DAC Architecture With up to 56-GHz Sampling Clock and 6-VppDifferential Swing

Abstract

A distributed power digital-to-analog converter (DAC) architecture with multi-level segmentation is proposed. Due to its large output voltage swing, it can be used as a large swing arbitrary waveform generator suitable for a variety of wireline, fiber optic, and instrumentation applications. A proof-of-concept 56-GS/s 6-bit implementation with most significant bits (MSBs) and least significant bits (LSBs) segmentation and full-rate clock was manufactured in a production 130-nm SiGe BiCMOS technology. The circuit features 14 independent data bits—seven for the three MSBs and seven for the three LSBs—each running at up to at least 44 Gb/s. The measured saturated output power and bandwidth are 17 dBm and 45 GHz, respectively. An output swing of 3.4 ${\hbox{V}}_{\rm pp}$ per side is observed in 50- $\Omega$ loads. Spectral measurements demonstrate multi-bit modulation at carrier frequencies as high as 56 GHz. To the best of our knowledge, this marks the highest output-bandwidth highest voltage-swing current-steering DAC in silicon.