A novel approach for implementing ultra-high speed flash ADC using MCML circuits

We propose in this paper a new MOS current-mode logic (MCML) approach for implementing ultra-rapid and accurate comparators for flash ADC applications. The speed-to-power ratio of the MCML comparator is improved by a factor of 3 compared to CMOS latch counterparts. MCML is also used to build up the subsequent 6-bit flash decoder block which exhibits better performance than the fastest published 6-bit CMOS decoder. A 6-bit full-flash ADC has been implemented and sent to TSMC for fabrication in 0.18-μm CMOS. Post-layout simulations show that the ADC operates at 1.25 GHz, with an effective resolution bandwidth (ERBW) near 600 MHz.