A 630MHz, 76mW, Direct Digital Frequency Synthesizer Using Enhanced ROM Compression Technique

The paper presents a detailed description of a direct digital frequency synthesizer (DDFS) based on a Multipartite Table Method (MTM) which is a salient lookup table compression technique. A novel algorithm to find the optimal MTM decomposition which minimizes the ROM size while archiving a target spurious free dynamic range (SFDR) is presented in the paper. The DDFS designed with the proposed technique is ideally suited for a high clock frequency operation, requiring small lookup tables and simple multi-operand adders. Low-power operation is achieved through a power-driven synthesis, by using in the circuit two flip-flop topologies (with different power and delay performances). A test chip has been realized in 0.25 um, 2.5 V technology. The circuit achieves a 90 dBc SFDR and operates at a maximum clock frequency of 630 MHz, with 76 mW power dissipation. By reducing the power supply at 1.8 V, a maximum operating frequency of 430 MHz was measured, with a total power dissipation as low as 24.9 mW