Wide Range of Output Frequencies Differentiates Fully Integrated Clock

Austin, Texas — Freescale Semiconductor Inc. demonstrated a programmable, high-frequency clock synthesizer to address customer needs with a flexible, easy-to-use timing solution this week at its Smart Networks Developer Forum in Frankfurt Germany.

OEMs are designing faster and more complex, high-availability systems for the server, computing, networking, and telecommunications industries. These new systems require critical timing solutions that support redundancy and detailed testing to enhance system reliability while reducing test and maintenance time. To address this growing market need, Freescale has introduced a fully integrated clock synthesizer solution designed to facilitate and simplify clock redundancy and programmable frequency design.

The MPC92432 high-frequency synthesizer is an I2 C programmable clock source that gives designers the flexibility of using a single clock chip to generate clock frequencies from 21.25 to 1360 MHz. The MPC92432 synthesizer delivers cost-effective frequency margining capability to traditional clock trees with low power consumption. The synthesizer is designed as an ideal interface to the MPC9894 Intelligent Dynamic Clock Switch (IDCS) for a multiple-redundancy and frequency margining timing solution. The MPC92432 uses Freescale's silicon-germanium-carbon (SiGe:C) technology to achieve exceptional price/performance in combination with low power consumption.

Freescale developed the MPC92432 SiGe:C synthesizer in response to requests from high-availability server manufacturers for a fine-programmable device to drive the MPC9894 IDCS. Freescale worked closely with key customers in the server and computing industry to develop this synthesizer product. The device can be used in any system that requires an accurate, adjustable frequency.

The fine granularity of the synthesized output frequency enables system marginality testing to be performed prior to release and solidifies system performance parameters, thus reducing test cost and test time. The MPC92432 is fully programmable through an I2 C bus or through an alternative parallel interface. The device's I2 C command set allows easy, secure programming and monitoring of the synthesized frequency. The I2 C frequency increment and decrement commands are most effective in frequency margin and system test environments.

The MPC92432 clock synthesizer has the flexibility to accept either a low frequency, low-cost crystal or a LVCMOS-compatible reference clock signal. The device has two differential high-frequency LVPECL outputs designed for interoperability with other differential I/O. The lock status of the fully self-contained internal phase-locked loop (PLL) is indicated by a separate output signal and by an internal I2 C register flag, supporting system alarm functions.

“This latest clock synthesizer device provides an important solution to our customers' needs for higher performance systems and demonstrates our continued commitment to providing complete timing solutions,” said Bill Dunnigan, corporate vice president and general manager of Freescale Semiconductor's Computing Platform Division, Austin, Texas.

The MPC92432 device is now available for sampling with production quantities slated for the first quarter next year. Pricing is $4.66 in 10,000-piece quantities.

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MPC92432 Block Diagram
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The MPC92432 is Freescale's first programmable clock synthesizer with an I2 C system interface. Older products within this Freescale family of nine synthesizer devices had serial and parallel inputs used to configure output frequencies. This new device is programmable through an I2 C interface, a widely used, industry-standard serial bus interface defined by Philips Semiconductor in the 1980s.

There are several vendors with programmable clocks on the market, but I don't think there is anything available that can generate a clock signal over 1 GHz that is programmable, commented Susie Inouye, senior industry analyst with Databeans Inc., Reno, Nevada. “By being programmable, it enables OEMs to use this product in multiple application boards (end products), using multiple clock frequencies. The flexibility in output frequency also means that multiple OEMs within the whole market could be using the same device for difference applications in multiple segments. The wide range of available output frequency differentiates this part,” she said.

Some of the other players that have programmable clock synthesizers include Cypress Semiconductor, Integrated Circuit Systems, Micrel, Texas Instruments, and IDT.

The MPC92432 clock synthesizer allows customers to perform much more functionality testing within the system, said John Fairholme, director of Freescale's Timing Solutions Operation in Chandler, Ariz. The synthesizer has various adjustable dividers and multipliers, which allows designers to apply a fixed-input clock frequency and generate almost any output frequency required by their system. Customers can take a standard, inexpensive crystal, such as a 16-MHz device, and feed it into the MPC92432. This allows the output frequency to be programmed over a wide frequency range of roughly 21 MHz to more than 1.3 GHz. This frequency range covers clock requirements for such applications as workstations and networking equipment. “You can increment the frequency in very small steps so a customer can use this part with a simple crystal and create any frequency output they wish,” Fairholme said.

The new device covers the widest frequency range in the Freescale synthesizer portfolio, Fairholme said. “Other synthesizer products in the market cover parts of the frequency range but are less compatible with new in-system programming trends. By using our new device's I2 C interface, you can build the synthesizer into your system and then use the software interface to change the frequency to margin the system beyond the specified operating range. Generally, as clock rates increase, timing budgets get tighter and the system functioning at high speed is very critical. Evaluating the system at wide range of operating speeds assures overall system performance in the application environment.”

The MPC92432 device's I2 C interface enables easy software control from a maintenance processor. This capability was possible in the past, but it was a very manual-intensive way of adjusting system frequencies.

The MPC92432 uses Freescale's silicon-germanium-carbon (SiGe:C) process technology, which gives Freescale the capability to cover the wide frequency range of 21.25 MHz to 1.36 GHz. “The technology can support a very fast PLL with voltage-controlled oscillator (VCO) frequencies of up to 2.7 GHz. This frequency is then scaled down to the desired system operating frequencies,” Fairholme explained. Many CMOS processes won't go that fast, he added.

The MPC92432 can facilitate a reduction in the bill of materials, giving designers the flexibility of using a single clock chip across many system designs. Many clocks today will provide outputs at a very limited frequency range, requiring system manufacturers to stock a variety of clocks to cover their portfolio requirements. Now developers can use the same chip for many applications, Fairholme said.

For developers concerned with having a high availability system that can run 24 hours a day, 7 days a week, Freescale designed the MPC92432 synthesizer to work with its MPC9894 IDCS. Developed about two years ago, the MPC9894 is priced at $5 to $7, depending on volumes. The MPC9894, a redundant clock generator, is also programmable through an I2 C interface and maintains a glitch-free clock environment supporting up to four backup clock sources. Used in combination, these Freescale devices enable systems to continue operating even when one of a number of multiple clock sources fail, Fairholme said. “If a customer has a board failure, he can pull the board out and the system will keep running based on another backup clock source,” he explained.

Freescale plans to offer future clock synthesizer products that include more outputs and spread spectrum capability. Spread spectrum reduces system electromagnetic interference (EMI) by spreading the clock energy over a range of frequencies, Fairholme said.

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