Precise free-running period synthesizer (FRPS) with process and temperature compensation

This paper proposes an all-digital, automated, clock generator based on a free-running oscillator that can generate arbitrarily precise frequencies. The entire system can be implemented using standard cells and even has a compensation system to mitigate the effects of environmental variations on frequency. The design is implemented in VHDL and synthesized using Artisan standard-cells in TSMC´s 180 nm CMOS technology. Post-layout timing analysis shows that the proposed free-running period synthesizer (FPRS) can operate at a frequency of up to 175 MHz. The architecture was also validated with an implementation on a Xilinx´s Spartan 3 FPGA that works at 80 MHz. In both implementations, the worst case peak to peak jitter of the output clock is equal to one period of the free-running oscillator.