News and New Products

Stable quartz oscillator uses SAW technology

By Paul Rako, Technical Editor -- EDN, 10/13/2009

Targeting LAN (local-area networks) and SAN (storage-area networks), Epson Toyocom recently announced the highly stable EG-4101/4121CA SAW (surface-acoustic-wave) resonator. The part combines low jitter, low phase noise, high stability, and temperature coefficients better than those of AT-cut quartz crystals. The resonator offers a frequency tolerance of ±50 ppm and maximum phase jitter of 0.2 psec at 622 MHz over a 12-kHz to 20-MHz bandwidth. The device is available with LV-PECL (low-voltage-positive-emitter-couple-logic), LVDS (low-voltage-differential-signaling), and HCSL (high-speed-current-steering-logic) outputs. Available frequency ranges are 100 to 700 MHz for the LV-PECL- and LVDS-output versions and 100 to 500 MHz for the HCSL version. The resonator has a supply voltage of 2.5 to 3.3V, and current consumption ranges from a maximum of 30 or 45 mA over the supply-voltage range for the LVDS version to 80 or 100 mA for the LV-PECL version.

SAW resonators and oscillators differ from SAW filters in that the resonators use a quartz rather then a ceramic element. Don’t confuse saw resonators with inexpensive silicon or ceramic resonators, which tend to have much lower Q (quality factor) and worse initial accuracy and temperature coefficients. Because the SAW resonators operate at their fundamental-resonance mode, they lack the frequency jitter of conventional crystal oscillators that operate at a lower frequency; a PLL (phase-locked loop) then multiplies that frequency inside the chip. The operation at fundamental mode also means that the parts do not frequency-hop as quartz crystals do.

The EG-4101/4121CA operates over a standard temperature range of −40 to +85°C or an optional range of −40 to +90°C and comes in a 7×5×1.2-mm package. It sells for $12 to $18 (1000) and is available for sampling now; volume production will begin in the second quarter of 2010.