The robust voltage-oscillator is presented by using the constant current reference and the ring oscillator for the embedded system application.The constant current reference generates the constant current for the succeeding ring oscillator to produce a stable 4MHz oscillation frequency.The proposed VOC circuit was fabricated in a 0.35 um CMOS technology and worked with a supply voltage of 3.3V.The chip area of the VCO was 150 um x 130 um.According to measured results, the oscillator frequency drift of proposed VCO was 986 ppm/℃ over a temperature range of -25℃ to 100℃.The phase noise of -62.29 dBc/Hz was obtained at 1MHz offset from the carrier.Moreover, total current consumption of the entire VOC was 234.72 uA. Therefore, the proposed VCO is suitable for integration into the embedded system.
