Clock chips boast subpicosecond jitter

A new series of clock ICs aims to meet the most rigorous signal-processing requirements in today's high-performance electronics applications.

A new series of clock ICs aims to meet the most rigorous signal-processing requirements in today's high-performance electronics applications, such as wireless infrastructure transceivers, instrumentation and broadband infrastructure.

Within these applications, signal processing schemes are reaching astounding speeds, and jitter, or the uncertainty of the clock edge, can cause transmission errors and have an adverse effect on a system's overall performance.

ADI's new clock ICs feature ultra-low-jitter performance (subpicosecond), which enables the devices to deliver an extremely clean system clock for significant noise reduction in system-critical signal chains.

In addition to low jitter, ADI's clock ICs improve system performance through the integration of several key functions that eliminate the need for multiple discrete components, reduce board space, and ultimately reduce BOM (bill of materials) costs.

These features include a low-phase-noise PLL (phase locked loop) frequency synthesiser core, programmable dividers, and adjustable delay blocks.

Combined with subpicosecond jitter performance, these features make ADI's clock ICs the industry's best at maximising the performance of critical-signal-path components, such as analogue-to-digital convertors (ADCs), digital-to-analogue convertors (DACs), direct digital synthesisers (DDSs) and mixed-signal front end (MxFE) devices.

"As the industry leader in data conversion, ADI continually seeks to provide customers with the highest levels of system performance, and ADI's clock ICs are key to improved system performance", said Kevin Kattmann, Product Line Director, High-Speed Convertors, Analog Devices.

"As frequencies and datarates move higher and higher, the accuracy of a system and the performance of its convertors is increasingly limited by the quality of the clock signal".

"ADI's new series of clock ICs combines best-in-class signal integrity with innovative functionality, allowing customers to achieve optimum system performance, while greatly simplifying the clock tree design task".

ADI's clock IC offerings include both clock distribution and clock generation devices.

ADI's clock distribution IC series includes the AD9510, AD9511 and AD9512.

These devices feature subpicosecond performance over a broad frequency range, higher levels of integration and more programmability than other solutions.

Low phase noise and low jitter are key to reducing overall noise in a signal path.

ADI's clock distribution ICs feature LVPECL outputs, as well as user-selectable LVDS and CMOS options: LVPECL outputs operate to 800MHz with additive jitter less than 250fs RMS; LVDS and CMOS outputs operate up to 800 and 250MHz, respectively; and in both LVDS and CMOS modes, the additive jitter is less than 300fs RMS.

The voltage levels for both LVPECL and LVDS clock outputs are programmable, allowing the system designer to determine the best voltage swing for a given application.

The AD9510 offers the most flexibility, mixing LVPECL, LVDS and CMOS logic for a total of eight independent clock outputs.

For designs requiring fewer outputs, the AD9511 and AD9512 pack five independent outputs into a smaller package at reduced power consumption.

ADI's clock distribution ICs eliminate the extra components required to generate gate delays and phase shifts, by using dividers with dramatically increased functionality.

Each clock divider is programmable to any integer ratio from 1 to 32, offering flexibility when handling multiple frequencies on one PCB.

The divide function also includes a user-selectable offset word that enables channel-to-channel phase control.

Because the devices perform phase control inside the divider block, they maintain much lower jitter than equivalent discrete implementations.

ADI's clock distribution ICs feature on-chip programmable delay allowing users to adjust for set-up and hold-time requirements between data convertors and digital ASICs, FPGAs and digital up/down-convertors, without adding extra clock hardware.

All three AD951x products include at least one fine-delay-adjust channel with a programmable full-scale range from 1 to 10ns.

A 6bit delay word offers 64 unique delay settings with step sizes as low as 16ps.

Both the AD9510 and the AD9511 integrate a low-phase-noise, 1.5GHz PLL frequency synthesiser core on chip.

The PLL is optimised for clock applications and consists of a programmable reference divider, a low-noise phase frequency detector, a precision charge pump, and a programmable feedback divider.

For applications that do not require an on-chip PLL, the AD9512 offers two 1.5GHz clock inputs and five independent clock outputs.

The AD9510 is sampling now with production quantities available in February 2005.

The AD9511 and AD9512 begin sampling in December 2004 with production quantities available in March 2005.

The AD9510 is offered in 64-lead LFCSP (lead frame chip scale package) and is priced at $11.95 per unit in 1000-piece quantities.

All three AD951x products are specified to operate over the extended industrial range of -40 to +85C.

In addition to clock distribution, ADI also supports clock generation with the AD9540, released earlier this year.

Specifically designed to support the stringent clocking requirements of high performance data convertors, the AD9540 clock generator helps reduce system cost and provides valuable flexibility.

The AD9540 features high-performance PLL circuitry, including a flexible 200MHz phase frequency detector and a digitally programmable charge pump current.

The device also provides a low-jitter (less than 700fs RMS), 655MHz CML mode (PECL compliant) output driver with programmable slew rates.

External VCO (voltage-controlled oscillator) rates up to 2.7GHz are supported.

Extremely fine frequency tuning resolution (48bit tuning word) and 14bit phase adjustment enable ultra precise control of the output's phase and frequency.

The AD9540 is specified to operate over the extended industrial range of -40 to +85C.

The AD9540 is available in full production and is offered in a 48-lead LFCSP.

It is priced at $9.95 per unit in 1000-piece quantities.

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