MMD Components (Monitor & Quartztek), a producer of frequency control devices, has introduced the smallest quartz crystal available in production quantities.  Measuring only 2 x 2.5 millimeters, with an ultra-low 0.57-millimeter profile, MMD’s new X series is a surface-mountable crystal that can be used in any application where space is limited and a frequency reference required, such as Bluetooth devices, PDAs, cell phones and MP3 players.          X series crystals are available with a wide frequency range of 16 to 60 MHz and a frequency tolerance/stability rate as high as ±50 PPM/±100 PPM.  The units are fully RoHS compliant and compatible with Pb-free reflow profiles; feature ruggedized construction for extreme vibration and shock applications, allowing fundamental-mode operation to 60 MHz; and can operate in temperatures as high as 70ºC.           Hermetically sealed in a 4-pad ceramic package, the crystals are delivered on tape and reel for easy pick and place.