A radiation-hardened DLL with fine resolution and DCC for DDR2 memory interface in 0.13 μm CMOS

This paper presents a radiation-hardened-by-design digital delay locked loop (DLL) for DDR2 memory interface. The DLL utilizes thermometer coding with bubble correction and phase combination to cope with single event effects (SEEs). In addition, phase interpolation and duty cycle corrector are employed to achieve both high resolution and low duty cycle distortion. The proposed DLL is designed and simulated in a 0.13 μm CMOS technology. Simulation results show that the DLL is hardened against SEEs for charge injection as large as 250 fC and can recover quickly from radiation strikes on its sensitive nodes. The DLL operates at 267 MHz with 10% input duty cycle distortion and 30 ps delay resolution. It consumes 6.3 mW of power under 1.5 V power supply.