Charge pump‐ and VCO‐based second‐order delta‐sigma ADC

Abstract

A low-power charge pump-and VCO-based delta-sigma ADC is presented, realising second-order noise shaping without any analogue integrator. The proposed synchronous pulse-width modulator-driven charge pump replaces an analogue integrator in delta-sigma ADC power efficiently. Together with the noise shaping provided by the VCO in the quantiser, an analogue-less 2nd-order delta-sigma ADC is obtained. The simulation results in 90 nm CMOS show that the proposed charge pump-and VCO-based delta-sigma ADC achieves 78.7 dB signal-to-noise ratio and 74.2 dB signal-to-noise and distortion ratio for a bandwidth of 2 MHz, consuming 2.95 mW, corresponding to a FoM of 0.18 pJ/conv.

Fully‐VCO‐based 0‐2 MASH CT ΔΣ ADC

“…A noise-shaping time-to-digital converter is inserted between a VCO-based quantiser and a feedback DAC to implement second-order shaping without analogue amplifier [4]. Also a pulse-width modulation (PWM)-controlled charge pump is proposed as a substitute of front-end analogue integrator [5]. In [6,7], VCOs and digital counters are used to build high-order amplifier-free ΔΣ ADCs.…”