A Single-Trim Frequency Reference System With 0.7 ppm/°C From −63 ◦C to 165 ◦C Consuming 210 µW at 70 MHz Alexander S. Delke

Abstract

This article presents a frequency reference system that combines high frequency accuracy and low power consump- tion using a single-point temperature trim and batch calibration. The system is intended as a low-cost fully integrated crystal oscillator replacement. In this system, the oscillation frequency of a power-efficient, but process, voltage, temperature (PVT) and lifetime (L)-sensitive current-controlled ring oscillator (CCO) is periodically (re)calibrated by the well-behaved frequency stability of an untuned LC–based Colpitts oscillator (LCO), which is optimized for stability over PVT variations and lifetime (PVTL). During the single-point room temperature factory trim, the frequency of the LCO is determined and the result is digitally stored. An on-chip calibration engine tunes the CCO to the target frequency based on the LCO frequency, temperature sensor information, and digitally stored trimming information, thus effectively improving the frequency stability of the ring oscillator. The relatively high-power LCO is heavily duty-cycled to minimize the overall power consumption. A prototype fabricated in a 0.13-µm high-voltage (HV) CMOS SOI process and assembled in a plastic package demonstrates an inaccuracy lower than ±93 ppm over a temperature range from −63 ◦C to 165 ◦C across 18 samples. The presented frequency reference system, including on-chip voltage regulators and a temperature sensor, occupies a chip area of 0.69 mm 2 and consumes about 64 µA from a single 3