A 2.9mW, +/− 85ppm accuracy reference clock generator based on RC oscillator with on-chip temperature calibration

A novel on-chip frequency calibration of temperature dependency is proposed for CMOS reference frequency generator. High-order temperature coefficients are rapidly extracted by employing a carefully designed on-chip heater, so that the frequency deviation due to the temperature variation is accurately estimated, and compensated in digitally by means of all-digital PLL (ADPLL). The proposed technique was implemented in a 0.18um CMOS and achieved ±85ppm accuracy at 24MHz, consuming a power of 2.9mW.