News and New Products

Silicon and quartz combine for advanced crystal entity

By Bill Schweber -- EDN, 5/26/2005

Crystals are the heartbeats of today’s synchronous circuits, but they face the challenge of reliably hitting and sustaining higher clock rates. According to Pericom/Saronix, its S1614XP and S1613XP series of oscillators promises to improve that reliability by reducing the need for thin, fragile quartz elements that higher frequencies otherwise demand. Saronix Product Marketing Manager Brandon Ogilvie says, “The products use a thicker quartz blank paired with a non-PLL, patent-pending [upconversion] design.” The company expects the new technology to reduce failure rate by 75% and that its approach yields lower cost and comparable performance to conventional, overtone-based legacy approaches.

The oscillators operate from 100 to 160 MHz. Computed phase jitter is 0.5 psec at a 1-sigma-rms level, and total stability is at least ±25 ppm for the commercial range and ±50 ppm for the industrial range. These specs make the device suitable for sensitive applications, such as 1- and 10-Gbps Ethernet, Fibre, Fibre Channel, Serial Attached SCSI, and others. The 2.5/3.3V (30 mA) units are compatible with LVCMOS/LVTTL signals. They are available at standard, common operating frequencies in a 5×7-mm ceramic package, and prices begin at $1.25 (10,000).

Not all applications need the Pericom unit’s performance. Suiting those uses, Linear Technology’s LTC6905xx silicon-oscillator family has typical jitter of 50 psec at 170 MHz and stability of 20 ppm/°C but has lower current consumption: a maximum of 12 mA at 100 MHz. It is also, at 3×3 mm (SOT-23), smaller than the Pericom device. It starts up in 100 μsec—a critical factor in many low-power applications in which shutdown is the norm—and duty-cycle variation is just ±2.5%. It is available with any of four master clock frequencies of 80 to 133 MHz and includes circuitry to divide the clock by one, two, and four for a wide range of possible outputs. For factory- or field-adjustment situations, the IC is also available in a resistor-programmable version. It sells for $1.15 (1000).

Pericom Semiconductor Corp, www.pericom.com.

Linear Technology Corp, www.linear.com.