A reference voltage programmable 6-bit differential delay-line ADC for digitally controlled DC-DC switching converters

This paper presents the design of a 6-bit, 25 Msps, reference voltage programmable delay-line Analog-to-Digital Converter (ADC), which is aimed to use in the digitally controlled DC-DC switching converters. A new differential bias circuit is used to improve the linearity of delay cells and also the ADC. The reference voltage can be adjusted from 1.8 V to 2.5 V with 0.2 V step, and the input voltage range is limited within ±200mV around the reference voltage. This ADC is implemented in 0.18um CMOS process and works at 3.3 V power supply. The simulation results for this ADC show that, the power dissipation is 450 uW, ENOB is 5.96-bit, DNL and INL is less than ±0.55 LSB and ±0.42 LSB, respectively. The designed ADC has the power-and die area-efficiency, it can be used as the built-in ADC of the digital controller in the digitally controlled DC-DC switching converters.