A 250MHz direct digital frequency synthesizer with /spl Sigma//spl Delta/ noise shaping

摘要

A 14b direct digital frequency synthesizer in 0.25/spl mu/m CMOS uses a 2b second-order /spl Sigma//spl Delta/ modulator. The /spl Sigma//spl Delta/ noise shaping significantly reduces spurs caused by phase truncation and the measured SFDR is <110dB. The prototype IC consumes 100mW with a 2.5V supply and works to 250MHz.