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This article presents a frequency reference system that combines high frequency accuracy and low power consumption 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- μ m 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 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 μ A from a single 3.3-V supply. The frequency error due to supply variation is roughly 92 ppm/V. The mean frequency shift due to aging, measured before and after a six-day storage bake at 175 ∘ C, is only 52 ppm.

A single-trim, highly accurate Colpitts-based frequency reference is presented. Our analysis shows that the Colpitts-topology outperforms the cross-coupled LC -topology in terms of temperature stability. Measurements on prototypes in a 0.13- $\mu \text{m}$ high-voltage CMOS silicon on insulator (SOI) process were carried out from −50 °C to 170 °C. Based on sample-specific single room temperature trim and batch calibration, our frequency reference achieves an accuracy of ±120 ppm for 16 samples from a single wafer utilized for extracting the batch-calibration polynomial and ±300 ppm for 48 samples across three wafers from the same batch. This is a 4 $\times $ improvement over related single-trim state-of-the-art solutions. Frequency drift due to aging, tested after a six-day 175 °C storage, is below 100 ppm. The oscillator core dissipates 3.5 mW from a 2.5-V supply and has 220-ppm/V supply sensitivity without supply regulation.

The characterization of a human fibroblast surface glycoprotein, visualized by crossed immunoelectrophoresis using rabbit antibodies against whole fibroblasts, is described. The antigen is synthesized by fibroblasts in culture and was localized both intracellularly and at the cell surface. It was highly antigenic and was detected only in human cells of mesenchymal origin. The glycoprotein occurred in two different forms with alpha 2 and beta electrophoretic mobility. The slow migrating amphiphilic beta form was localized at the cell surface and showed a single protein band with an apparent molecular weight of 150 000 in SDS-polyacrylamide gel electrophoresis. By external papain treatment of intact viable cells, a water-soluble molecule was released with a reduced molecular weight (140 000) and an increased electrophoretic mobility as compared to the native membrane component. This hydrophilic form was also present intracellularly in fibroblasts not treated with exogeneous proteases. The observation that the detergent-solubilized beta form was irreversibly converted to a more anodic form by incubation of whole cell extract at acidic pH, suggested that the intracellular protein represented a lysosomal degradation product of native internalized fibroblast surface glycoprotein.