A new feedback circuit based charge-pump for wide-range and low-jitter DLL suitable for PET imaging applications

Abstract

Charge-pump adds/removes charges to/from a loopfilter via constant current source/sink. Channel length modulation effect in the locking range of DLL (Delay Locked Loop) worsens the matching between this current source and sink. A new feedback circuit based charge-pump is proposed here to reduce this mismatch for PET (Positron Emission Tomography) imaging applications. Simulations are performed in UMC 180nm process to validate the effectiveness of the technique. Here current mismatch reduction of 28.08% and 86.25% is achieved for bias current of 10 uA and 40 uA respectively at 3.3V supply. Locking range of DLL is enhanced by (Vtn + Vtp + 2Von) compared to the existing feedback circuit in literature. The advantage of the feedback circuit is also observed at lower supply voltages viz. 2.5V and 1.8V at 180 nm technology node.