Dual-Modulus Prescaler Based on Transmission Gates and Pseudo-PMOS Logic

The Dual Modulus Prescaler is a critical block in CMOS systems like high speed frequency synthesizers. The design of high divide-by-value, high speed and low power dual modulus prescaler, however, remains a design challenge. In order to face the challenge, this paper introduces an idea of using transmission gates and pseudo-PMOS logic in realization of the dual modulus prescaler. The topology of the prescaler proposed in this paper is different from the prior designs primarily in two ways: (i) it uses transmission gates in the critical path and (ii) the D-flip flops used in the synchronous counter are comprised of pseudo-PMOS invertors and ratioed latches. A design of the pseudo-PMOS logic based DFF is introduced and used in the proposed prescaler design. Based on the proposed topology, a dual-modulus divide-by-127/128 prescaler is implemented in 0.35 m CMOS technology. Its maximum operating frequency is observed as 2.4 GHz. It consumes 4.8 mW power from a 3 V supply. Circuit operations and measurement results are provided. The silicon estate required is only 0.06 mm². There is no flip flop and logic gate in the critical path. The proposed topology is suitable firstly for the high speed and high divide-by-value prescaler designs. Secondly, it reduces: (i) design complexity, (ii) power consumption and (iii) load to preceding circuit.