This paper describes the design and implementation of an asynchronous clock generator which has been used in a 14-bit two-stage pipelined SAR ADCs for low-power sensor applications. A self-synchronization loop based on an edge detector was utilized to generate an internal clock with variable phase and frequency. A tunable delay element enables to allocate the available time for the switch capacitor DACs and the gain-stage. Thereafter, three separate asynchronous clock generators were implemented to create the control signals for two sub-ADCs and the gain-stage between. Finally, a 14-bit asynchronous two-stage pipelined SAR ADC was designed and simulated in 0.18 μm CMOS. Detailed pre-layout circuit simulations show that the ADC achieves a SNDR of 83.5 dB while consuming 2.13 μW with a sampling rate of 10 kS/s. The corresponding FoM is 177.2 dB.
['Kairang Chen', 'Martin Nielsen-Lonn', 'Atila Alvandpour']
Asynchronous clock generator for a 14-bit two-stage pipelined SAR ADC in 0.18 μm CMOS