High frequency stability TCXO targets GPS applications

Highlighting the way that oscillators are evolving to meet the needs of wireless applications, Epson Toyocom's latest temperature-compensated crystal oscillator (TCXO) is small enough, and boasts a frequency stability high enough, to meet the needs of GPS applications in mobile terminals.

Epson has seen growth in demand for frequency-stable TCXOs, which are used to ensure accurate positioning, largely as a result of the popularity of location-aware services in mobile phones with built-in GPS functionality, and from personal navigation devices (PND). The TG-5025BA, which will be made available in a 2.1mm by 1.7mm package for February 2009, suits these applications.

Though 36% smaller in footprint than its predecessor, the TG-2520, the TG-5025BA has a frequency-temperature coefficient (an indicator of frequency stability over a temperature range) of 0.5 x 10-6, the equivalent rating to a TCXO in a conventional package size.

The TG-5025BA is among the first TCXOs to employ the company's photo AT chips, fabricated using Epson's QMEMS process. The QMEMS technology enables Epson Toyocom to make ultra-miniature photo AT chips that, despite their size, are said to be frequency stable and have nearly uniform characteristics, meaning that variation is limited. In the past, steps taken to limit variation in the characteristics of crystal oscillating elements adversely affected crystal characteristics and hindered production efficiency. For example, variations were offset by tuning oscillation circuits according to the characteristics of each crystal chip.

This oscillator promises high reliability thanks to the use of internal wire bonding and the way the ic is packaged. The crystal unit, encased in a ceramic package, is sealed together with an oscillation circuit in a molded plastic housing. This structure reduces the susceptibility of frequency to changes in ambient temperature.

Lost and found? Personal navigation devices

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