Second-order ΔΣ Modulator Research Articles

A high-pass shaped LMS algorithm based predistortion technique for fractional-[formula omitted] BB-DPLLs

In this paper, we prove that rather than the second-order ΔΣ modulator (DSM) as typically believed using the first-order one yields a faster convergence for the linear-piecewise predistortion technique employed in digital/time converter (DTC) based fractional-N Bang-Bang digital phase-locked-loops (BB-DPLLs). We also propose a novel technique that addresses the limit-cycle issue happening in near-integer channels of the conventional BB-DPLLs. With the first-order DSM-based novel technique, simulation results show that the worst fractional spurs are below −83 dBc at 12 kHz offset frequency assuming the DTC’s integral nonlinearity error is as large as 5 least-significant-bits.

A Dynamic Source-Follower Integrator and Its Application to .DELTA..SIGMA. Modulators

A switched-capacitor integrator based on dynamic source follower amplifiers has been proposed. Integrator operation has been confirmed and analyzed by assuming 0.18-µm CMOS technology. The integrator can reduce the number of elements considerably compared with conventional ones using operational amplifiers. As a result, the power dissipation of proposed integrator can be reduced to approximately one-eighth that of conventional integrators. The integrator is applied to a second-order ΔΣ modulator, and its successful operation has been confirmed by transistor-level circuit simulation.

A spread-spectrum clock generator for 6-Gbps Serial ATA transceiver

A transmitter-side spread-spectrum clock generator (TX-SSCG) with a second-order ΔΣ modulator is proposed for a 6-Gbps Serial ATA. Mixed-mode simulations show that a second-order ΔΣ modulator in TX-SSCG reduces the random jitter component of the receiver-side tracking skew through quantization noise shaping. Deterministic jitter is reduced with the loop bandwidth of RXPLL. A 0.13-µm CMOS prototype chip shows that the transceiver operates at 6Gbps over an 8-m SATA cable in TX-SSCG on and off. With TX-SSCG on, the spectrum is down-spread with 11.7-dB peak reduction and 5000-ppm spread amount.