Telephonics Corporation, a wholly owned subsidiary of the Griffon Corporation, announced today its integrated circuit ('IC') subsidiary, TLSI Inc., introduced the T277, a miniature, high precision Voltage Controlled Crystal Oscillator (VCXO) Clock Generator IC.

The T277's small size, low cost and stable clock reference make this device ideally suited for state-of-the-art handsets, routers, hubs, PCs, telephony and/or cable modems, set-top boxes and numerous other data transmission devices where cost, size and power need to be minimized and accuracy optimized.

First in a series of VCXO ICs, the T277 was designed to exhibit extremely low jitter and low phase noise performance (less than -140dBc/Hz at 100kHz offset from Fc). The integrated circuit utilizes a fundamental crystal to generate output frequencies from 8Mhz to 100Mhz.

"The T277 was designed to become the de-facto standard for low noise and high accuracy gigabit Ethernet and SONET applications," states Barry Eckstein, President of TLSI. "This advanced single chip solution maximizes system performance for the precise transmission and processing of data," said Eckstein.

The device incorporates a programmable divider that also allows users to select output frequencies lower than the crystal frequency while maintaining 50% output symmetry. Typical tuning frequency range is +/- 200 PPM (crystal and varactor dependent). Future products slated to be introduced include: a 200MHz VCXO IC and a 650MHz VCXO IC that will incorporate PECL and LVDS outputs.

Additional features of the T277 include: operating supply voltage 3V to 5.5V, operating temperature range -40ºC to +85ºC, power less than 150mW, start-up time less than 5 mS, rise and fall times less than 3 nS, nominal output duty cycle 45% to 55%, output drive capability of 50pF, tuning input impedance 50kW and internal crystal load capacitance 20 pF.

TLSI, Inc., 770 Park Avenue Huntington, New York 11743. Phone: 631-755-7005; Fax: 631-755-7626. Web - www.tlsi.com

Networking and telecommunications customers are pushing manufacturers with demands for higher frequency components. Unfortunately, it is difficult to provide these components without degrading phase noise and stability. You know this if you are designing some of today's wireless systems and you also know you need low jitter circuit components. Critical timing components are necessary, such as clock oscillators and VCXOs, to achieve control over jitter performance. These VCXOs are very accurate devices that maximize system performance with stable, low-noise clock reference for the precise transmission and processing of data.

The recently introduced VCXO Clock Generators from TLSI may be able to help your critical timing needs as it is suited for a wide range of applications that need reduced size, power, and the number of discrete components. Although the T277 doesn't have the best specs (remember that everyone doesn't use the exact same parameters to define specs) compared to other manufacturers, it does however have some impressive numbers when looked at overall. For example, the T277 chips exhibit excellent temperature stability at +/- 15 ppm and phase noise performance of -140 dBc/Hz, at 100 kHz offset. Additionally, typical jitter is 5 ps and typical rise/fall time is 3 ps. The average tuning frequency range is +/-200 ppm, which it should be noted, is crystal and varactor dependent. The company also provides an example to tell you exactly how they figured the pullability of the oscillator. For example, for a typical crystal, C = 0.02 pF and CO (parallel capacitance of the filter) = 5 pF. Using a Hyperabrupt Tuning Diode, the typical capacitance of the diode is 12.3 pF at 1 volt and 2.60 pF at 3 volts. The varactor diode appears in series with the 20 pF internal chip capacitance. Additionally, assuming 2 pF stray board wiring capacitance across both the varactor and the chip terminals, the following calculations determine the pullability of the oscillator;
Frequency shift with 1 volt across the varactor diode:
C_P (the additional loading capacitance used to tune the crystal) = 20 pF + 2 pF in series with 12.3 pF + 2 pF = (22.0x14.3)/(22.0+14.3) pF = 8.67 pF
Δf1 = 0.02x10⁶/(2(5+8.67) ppm = 731.5 ppm

Frequency shift with 3 volts across the varactor diode:
C_P = 20 pF + 2 pF in series with 2.60 pF + 2 pF = (22.0x4.60)/(22.0+4.60) pF = 3.80 pF
Δf2 = 0.02x10⁶/(2(5+3.80) ppm = 1,136.4 ppm

Total Tuning Range = Δf₂ - Δf₁ = 1136.4 ppm - 731.5 ppm = 405 ppm

Another impressive tool that the company incorporates is a programmable divider that allows the user to select output frequencies lower than the crystal frequency while providing 50% output symmetry. The devices are available as die, probed wafers, or in SOIC surface-mount packages.

Finally, there are other high-performance VCXOs available in the small, surface mount 5 x 7-mm packages, and they charge extra for the smaller packaging. Maybe that's why I couldn't find any pricing for this chip.

Sample quantities of the T277 are now available. It is available in die as well as 8-Pin or 14-Pin SOIC packages.

Datasheet