Micrel’s MX55/57 FUSION crystal oscillator clocks push phase jitter down to 170 fs rms (12 kHz to 20 MHz). With an eye toward advanced communications, the oscillators handle frequencies ranging up to 840 MHz and support standard frequencies for 10/40/100G Ethernet, optical comm, SAS, and PCI Express. On-chip linear regulators enable high power-supply noise immunity. The devices support 3.3- or 2.5-V supplies and LVPECL, LVDS, CMOS, and HCSL output logic formats. They meet ±50-ppm total stability, including aging and temperature drift across a ‒40 to +85°C temperature range. In addition, their plastic molded assemblies help improve long-term reliability and minimize aging drift. The MX55 and MX57 come in 3.2- by 5-mm and 5- by 7-mm packages, respectively. Samples can be obtained through Micrel’s ClockWorks Configurator Web tool at http://clockworks.micrel.com/micrel.