High speed time-multiplexed continuous time Sigma-Delta converters

This paper presents a time-interleaved continuous time Sigma-Delta converter, which uses 4 identical channels clocked at equally shifted time moments of a 4 GHz clock. The data in each channel is filtered and afterwards recombined in a multiplexer, leading to an output signal at 4 GHz before decimation. Time-interleaving as proposed in this paper makes it possible to increase the signal-to-noise and distortion ratio (SNDR) in a specified bandwidth with 3 dB every time the number of channels is doubled. By exchanging the gain in accuracy for bandwidth, a high-speed Sigma-Delta converter with 250 MHz signal bandwidth and 65 dB SNDR is obtained in simulations. The simulated converter achieves a dynamic range of 72 dB and consumes 626 mW, leading to a Schreier FOM of 158 dB and a Walden FOM of 864.5 fJ/conv. This paper briefly discusses the different building blocks of the interleaved converter and their influence on the performance.