Voltage Scalable Zero-Crossing Based Pipelined ADC

A voltage scalable zero-crossing based (ZCB) pipelined ADC is built in 65nm GP 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 resolution. At 1.0V nominal supply and 50MS/s, the ADC achieves 67.7dB SNDR after calibration while dissipating 4.07mW resulting in an FOM of 41.0fJ/step. The supply voltage scalability is demonstrated down to 0.5V and improves the FOM to 28.0fJ/step, while maintaining higher than 66dB SNDR.