A 12b 5-to-50MS/s 0.5-to-1V voltage scalable zero-crossing based pipelined ADC

A voltage scalable zero-crossing based (ZCB) pipelined ADC is built in 65nm GP (general purpose) CMOS process and LP (low power) CMOS process. The highly digital implementation characteristic of the zero-crossing based circuit technique enables energy efficient operation and supply voltage scaling. A unidirectional coarse-fine charge transfer scheme is developed to allow low-voltage operation as well as high speed and high resolution. At 1.0V(GP) / 1.2V(LP) nominal supply and 50MS/s, the ADC achieves 67.7dB(GP) / 68.1dB(LP) SNDR after calibration while dissipating 4.07mW(GP) / 4.93mW(LP), resulting in an FOM of 41.0fJ/step(GP) / 47.5fJ/step(LP). The supply voltage scalability is demonstrated down to 0.5V(GP) / 0.8V(LP) and improves the FOM to 28.0fJ/step(GP) / 37.8fJ/step(LP), while maintaining higher than 66dB SNDR.