Review
As with most electronics, timing devices this year have been designed to deliver improved performance in a smaller package. In addition, some are being optimized for specific applications, such as 802.11a/b/g and Bluetooth.
Of the crystals we reported on this year, the NX2520DA series from Nihon Dempa Kogyo Co. Ltd., (ndk.com) was the smallest overall at just 2.5 mm x 2 mm x 0.6 mm. Available in fundamental frequencies from 20 to 80 MHz, the surface-mount quartz crystals have frequency tolerances ranging from ±10 to ±100 ppm over an operating temperature range of −10°C to +60°C. Standard operating frequencies for the series include 20, 22.5792, 24, 24.756, 26, 27, 28.63636, 32, 40, 44 and 48 MHz. Other operating specs include an equivalent series resistance (ESR) of 100Ù maximum over the 20-to-30 MHz frequency range and 50Ù from 30 to 80 MHz.
Targeting Bluetooth applications, the NX-3225DA quartz crystals, also from NDK measure 3.2 mm x 2.5 mm x 0.6 mm, weigh 17 mg, and come in frequencies from 16 to 55 MHz. Operating temperature is −10°C to 60°C. Drive level is 10 mW, with the crystals capable of withstanding 100 mW maximum.
On the oscillator side, the FOX923E from Fox Electronics (foxonline.com) measures just 3.2 mm x 2.5 mm x 1.2 mm. It's a temperature-compensated, voltage-controlled crystal oscillator (TCVC- XO) that is approximately 50% smaller than its predecessor. Frequency range is from 13 to 26 MHz with a frequency tolerance of ±0.5 ppm at 25°C ±2°. The oscillator operates on voltages from 2.85V to 3.15V and in temperatures from -20°C to 75°C. Other features include a frequency stability of ±2.5 ppm over the temperature range, a pullability of ±5 ppm to ±15 ppm at a control voltage of 1.5V ±1V, and input current of 2 mA at 3V/25°C.
From a performance standpoint, a line of differential PECL output oscillators from Pletronics (pletronics.com) deliver an ultra low jitter, e.g., 1-psrms maximum for >70 MHz and are suitable for use in Fibre Channel, SONET and Ethernet applications. The devices span frequencies from 10.0 to 650.0 MHz and have an input voltage of 2.5V, 3.3V or 5V. Frequency stabilities are ±20, ±25 and ±50 ppm over the operating temperature range of 0°C to 80°C.
An example of an oscillator optimized for IEEE 802.11 a/b/g wireless access points and WLAN enterprise networking equipment is the S1633 and S1634 series crystal clock oscillators from Saronix (saronix.com). The devices sport a small footprint of 3.2 mm x 5 mm in a ceramic package and are available in frequencies from 40 to 60 MHz with a symmetry of 45% to 50% or better. Other features include LVCMOS/LVTTL-compatible outputs, stabilities of ±25 ppm and ±50 ppm, low-power standby mode, and an operating temperature range from −20°C to +70°C. The S1633 series operates with a 3.3V supply while the S1634 operates from a 2.5V supply.
Other types of timing devices were not immune to the size-reduction tactics of manufacturers. For example, the ZL30462 from Zarlink Semiconductor (zarlink.com) was claimed as the industry's most compact timing module for high-speed line cards. Measuring just 1" x 1", the device packs both digital and analog PLL technology and a 20 MHz master oscillator. The tiny module is suitable for line cards in SDH/SONET edge equipment, such as media gateways, uplink systems, and edge switches, as well as in master timing cards for SDH access equipment. Clocking frequencies include jitter-attenuated 155.52-MHz LVPECL and 19.44-MHz CMOS, two 8-kHz frame pulses, and clocks operating at 2.048, 8.192 and 16.384 MHz.
—Joe Desposito
Outlook
Welcome To The Small Time
As with many other areas of electronics, you have to wonder how much smaller these crystals and oscillators can get. I suppose the answer for 2004 is "at least 50% smaller." This miniaturization trend is, of course, driven by electronics that are shrinking out of sight—cell phones come readily to mind. I believe the 2004 phones will be at least 50% smaller than the one you currently own. I recently attended an electronics function displaying consumer products for the 2003 holiday season. And sure enough, they were showing the Siemens SL56 cell phone, which is almost 50% smaller by volume than the size of my Motorola T730.
—JD
