Duty cycle measurement and correction using a random sampling technique

A specific value of duty cycle of an on-chip clock or signal often becomes of extreme significance in VLSI circuits like DRAM's, dynamic/domino pipelined circuits, pipelined analog-to-digital converters (ADC) and serializer/deserializer (SERDES) circuits, which are sensitive to the duty cycle or where operations are synchronized with both transitions of the clock. This paper introduces a novel idea based on a random sampling technique of inferential statistics for measurement and local correction of the duty cycle of high-speed on-chip signals. The high measurement accuracy achievable through the proposed random sampling technique provides a way to correct the duty cycle with a maximum error of less than half the smallest delay resolution unit available for correction. An input signal with duty cycle from 30% to 70% can be adjusted to a wide range of values within this range using a purely digital, area-efficient standard cell based design. Our experimental results gathered though extensive simulations of the proposed circuit manifest a very close correlation to the expected theoretical results.