A 1.8-V 22-mW 10-bit 30-MS/s Pipelined CMOS ADC for Low-Power Subsampling Applications

Abstract

This paper describes a 10-bit 30-MS/s subsampling pipelined analog-to-digital converter (ADC) that is implemented in a 0.18 mum CMOS process. The ADC adopts a power efficient amplifier sharing architecture in which additional switches are introduced to reduce the crosstalk between the two opamp-sharing successive stages. A new configuration is used in the first stage of the ADC to avoid using a dedicated sample-and-hold amplifier (SHA) circuit at the input and to avoid the matching requirement between the first multiplying digital-to-analog converter (MDAC) and flash input signal paths. A symmetrical gate-bootstrapping switch is used as the bottom-sampling switch in the first stage to enhance the sampling linearity. The measured differential and integral nonlinearities of the prototype are less than 0.57 least significant bit (LSB) and 0.8 LSB, respectively, at full sampling rate. The ADC exhibits higher than 9.1 effective number of bits (ENOB) for input frequencies up to 30 MHz, which is the twofold Nyquist rate (fs/2), at 30 MS/s. The ADC consumes 21.6 mW from a 1.8-V power supply and occupies 0.7 mm2, which also includes the bandgap and buffer amplifiers. The figure-of-merit (FOM) of this ADC is 0.26 pJ/step.