An All-Digital 90-Degree Phase-Shift DLL with Loop-Embedded DCC for 1.6Gbps DDR Interface

Abstract

An all-digital 90deg phase-shift DLL is proposed for 1.6 Gbps DDR interface by using a loop-embedded DCC and a binary phase detector with the lock range extended to 0~4pi radians. The DCC has a small delay and the fixed rising-edge property for loop-embedding. The chip fabricated with a 0.13 um CMOS process gives the DLL data rate of 667 Mbps~1.6 Gbps and the output duty cycle of 47.8%~49% for the input duty cycle of 23%~76%, at 1.6 Gbps and 1.2 V.