True 50% Duty-Cycle High-Speed Divider with the Modulus of Odd Numbers

Abstract

This paper proposes a true 50% duty-cycle highspeed prescaler with an odd modulus, based on current switchable D flip-flops. Each D flip-flop can sample data at the positive and negative clock edges, because of the changeable trigger mode. The proposed divide-by-N prescaler, with a 50% duty cycle, is formed as a ring with an N number of D flip-flops. Two types of 50% duty-cycle divide-by-five prescalers, the sample-hold-sample-hold-hold (SHSHH) prescaler and the sample-sample-hold-sample-hold (SSHSH) prescaler, are implemented using the 0.35 mu m SiGe HBT technology. The SHSHH divider has a better performance, up to 7 GHz, thanks to the synchronization of data and control signals.