Dual Time-Interleaved Successive Approximation Register ADCs for an Ultra-Wideband Receiver

Ultra-wideband radio requires Nyquist sampling rates of at least 500 MS/s with low resolutions. While flash is the traditional choice for these specifications, a comparative energy model is used to show the potential energy savings of the time-interleaved successive approximation register architecture, which requires only a linear number of comparisons versus exponential for flash. A dual 500-MS/s, 5-bit ADC chip is implemented in a 0.18-mum CMOS process, with both ADCs synchronized for use in an I/Q UWB receiver. Each ADC uses a 6-way time-interleaved SAR topology with full custom logic, self-timed bit-cycling, and duty cycling of the comparator preamplifiers to enable 500-MS/s operation with 7.8 mW power consumption. The output resolution is adjustable down to the 1-bit level for additional power savings