| IEEE IFCS May 2008 | Self-Referenced, Trimmed and Compensated RF CMOS Harmonic Oscillators as Monolithic Frequency Generators |
| Abstract: | Self-referenced, trimmed and temperature-compensated radio frequency (RF) CMOS LC, or harmonic oscillators (CHOs) are presented as high-accuracy and low-jitter monolithic frequency generators. CHOs are discussed within the context of recent efforts toward replacement of piezoelectric frequency references with silicon MEMS technology. In contrast, CHOs are self-referenced solid-state oscillators which can be fabricated in a standard microelectronic process technology. The CHO architecture and recent implementations are presented. Frequency- and time-domain performance of CHOs is reported and compared to the incumbent piezoelectric oscillators and emerging MEMS-referenced synthesizers. It is shown that CHOs achieve frequency error as low as plusmn26 ppm over 90degC and 1/6th the period jitter of MEMS-referenced synthesizers at the same frequency. |
| IEEE ISCAS 2008 | A 25MHz All-CMOS Reference Clock Generator for XO-Replacement in Serial Wire Interfaces |
| Abstract: | A 25 MHz all-CMOS clock generator is demonstrated where measured performance makes it suitable for direct replacement of the reference crystal oscillator (XO) for serial wire interfaces. Fabricated in a 0.25 mum 1P5M logic CMOS process, and with no external components, the developed clock generator dissipates 59.4 mW while exhibiting plusmn152 ppm frequency error over process, plusmn10% variation in the power supply voltage and from -5-75degC. Nominal period jitter and power-on start-up latency are 3.93 psrms and 268 mus respectively. |
| IEEE ISSCC 2008 | A 0.5-to-480MHz Self-Referenced CMOS Clock Generator with 90ppm Total Frequency Error and Spread-Spectrum Capability |
| Abstract: | The quartz crystal (XTAL) oscillator is one of the last components in electronic systems that has yet to be integrated. The advent of RF CMOS circuits and associated advances in CMOS process technology have enabled the development of low-noise integrated LC oscillators (LCOs), which are suitable for replacing XOs in USB applications. This work demonstrates a self-referenced CMOS LCO, or CMOS harmonic oscillator (CHO), that exhibits 90ppm total frequency error over process, bias and temperature, thus making it suitable for replacing XOs in many applications. Additionally, the clock generator can be configured to produce a number of different output frequencies, and includes a direct modulation technique enabling SSCG. |
| IEEE JSSC 2007 | A Monolithic and Self-Referenced RF LC Clock Generator Compliant With USB 2.0 |
| Abstract: | A monolithic and self-referenced radio frequency (RF) LC clock generator that is compliant with USB 2.0 is demonstrated in a system-on-chip (SoC). This work presents the first successful approach to replacing an external crystal (XTAL), the crystal oscillator (XO) and the phase-locked loop for clock generation in an IC supporting USB 2.0 using a standard CMOS fabrication process. It is shown that the primary design challenges with the implemented approach involve maintaining high frequency accuracy and low jitter. Techniques for addressing both are shown. In particular, the presented architecture exploits the effects of frequency division and low far-from-carrier phase noise to achieve low jitter. From a 1.536 GHz temperature-compensated LC reference oscillator, coherent clock signals are derived at 96 MHz for the SoC logic and 12 MHz for an on-chip full-speed USB PHY. Though self-referenced, approximately 400 ppm total frequency accuracy is achieved over process variations, 10% variation in the USB power supply voltage and temperature variation from 10 to +85°C. Measured period and cycle- to-cycle jitter are 6.78psrms and 8.96psrms, respectively. Fabricated in a 0.35µm CMOS technology, the clock generator occupies 0.22 mm2 and draws 9.5 mA from a 3.3-V supply, which is derived from the 5-V USB power supply. |
| IEEE CICC 2005 | A 9.2mW 528/66/50MHz Monolithic Clock Synthesizer for Mobile µP Platforms |
| Abstract: | A low-power monolithic clock synthesizer suitable for use in mobile µP platforms is presented. Clock synthesis is accomplished using an all-Si RF LC reference oscillator that does not require an external frequency reference. Fabricated in 0.18µm CMOS, the developed clock synthesizer demonstrates +1% frequency accuracy over process, voltage, and 0-70°C, exhibits 7.4/21/33psrms period jitter on 528/66/50MHz clock signals, and achieves a start-up latency of only 3.2µs. |
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