Web-based IC customization revolutionizes timing circuits

Web-based IC customization revolutionizes timing circuits

How the semiconductor industry will benefit with this transition

BY JAMES WILSON
Silicon Laboratories
Austin, TX
http://www.silabs.com

Clocks provide the electronic heartbeat for a wide variety of consumer electronics, communications, and computing applications. These timing components deliver critical reference frequencies to processors, FPGAs, ASICs, DSPs, ADCs, DACs, memory, and physical layer devices.

The combination of frequencies required in a given application can change dramatically based on component selection of the other ICs in the system, since each processor, FPGA or other device can have unique frequency requirements. In addition, timing requirements can vary considerably from application to application based on performance, processing, and line rate requirements.

Custom clocks for high-volume apps

To satisfy this diverse range of requirements, the timing IC industry has responded by developing application-specific clocks. Each device is highly customized to meet the frequency, jitter, phase, and skew requirements for a particular application. These ICs are simple pin-controlled devices and require no firmware or configuration via a host processor.

This traditional approach has two significant limitations. First, if the application’s frequency, jitter, or other performance requirements change, a new application-specific clock must be designed, manufactured, qualified, and tested. Sample lead times for clocks customized using dedicated wafer masks can approach eight weeks or more, which can be an issue in some time-sensitive designs.

Second and more important, application-specific clocks have traditionally only been available for high-volume applications. As a result, mid- and low-volume designs have resorted to using a combination of clocks, crystal oscillators (XOs), and crystals to complete their timing architectures. The resulting solutions are not optimized in terms of cost, power, or real estate.

Programmable clocks not optimized for performance or supply chain

To address this market need, several timing suppliers have introduced programmable clocks that can be in-circuit programmable through an I2 C interface. This ubiquitous microprocessor interface enables hardware designers to customize a clock for their given application.

This flexibility comes at a price, however. Jitter performance can vary significantly across frequency configurations. In addition, there are no guarantees that the clock can generate all timing references with exact (0-ppm) frequency synthesis error, forcing hardware designers to continue using crystal oscillators (XOs) in their designs.

Perhaps the most significant limitation of traditional programmable clock solutions is that they require I2 C-based firmware development. In many applications, an I2 C interface is either not available or not desirable. If the system has a single clock IC that is used as the master reference for the design, a chicken-and-egg scenario can potentially develop. The clock needs to generate the right frequency for the processor at startup, but in order to operate it must be programmed by the processor first. Often an XO must be used as the startup reference to solve this dilemma, increasing design complexity.

Field-programmable clocks are available that can be programmed on a socketed board using configuration software prior to installing the device in the end application. The process flow for procurement of field-programmed clocks is shown in Fig. 1 .

Fig. 1. Field-programmable clock process flow.

This approach is less than ideal because it is not scalable. Prototype quantities can be managed easily, but it is more difficult to support such a solution in volume production. This solution also requires a custom programming board and vendor-specific configuration software, and it forces customers to manage raw stock, device programming and finished goods stocking levels. Devices are not marked with a custom top mark, increasing the risk that a programmed device ends up on the wrong board.

Solving the problem: Web-customizable, programmable clocks

New generations of programmable clock generators are now available that address the deficiencies associated with traditional field-programmable solutions. These new timing products can be completely customized using Web-based utilities.

The process flow for Web-customizable clocks is illustrated in Fig. 2 . Using a simple point-and-click graphical user interface, a user can quickly configure the device input (crystal versus clock), input frequency and output frequencies. The utility assigns a unique orderable part number for each custom configuration. The developer can then order samples from the clock supplier directly online, and the customized clock products can be available in as little as two weeks after order placement.

Fig. 2. Web-customizable clock process flow.

The most significant benefit provided by Web-customized programmable clocks is that low- and mid-volume-based applications can finally enjoy the benefits of having fully customized, application-specific clocks. All frequencies can be synthesized from a single IC with 0-ppm frequency synthesis error, making it possible to replace multiple discrete clocks and oscillators with a single IC. All device customization, including custom part number assignment, device programming, custom part marking, and logistics can be handled by the supplier, freeing up hardware designers and procurement to focus on higher value-added activities.

To support Web-based device configuration, it is essential to have a highly flexible device architecture. For example, Silicon Labs’ Si5355 1 to 200-MHz clock generator has an architecture with four banks of clock outputs, and each of those banks is composed of two CMOS output clocks. Each bank can generate any frequency from 1 to 200 MHz, such that a single device can produce eight outputs at four unique, non-integer related frequencies.

All combinations of output frequencies are guaranteed to have 0-ppm frequency synthesis error. Since the Si5355 devices are pin-controlled, there is no need for I2 C firmware development and simplifying device startup. The device has consistently low jitter across all input/output frequency combinations (50-ps peak-to-peak period jitter), providing significantly lower jitter than traditional programmable clocks.

In addition, up to three unique frequency configurations can be customized per device, with external control pins available to select the active frequency plan. This enables one part number for a single device to replace three SKUs, simplifying inventory management.

An industry in transition

The advent of Web-customizable clocks represents a significant step forward for the semiconductor industry. ICs are manufactured in ultramodern, multi-billion-dollar wafer fabs and are created with state-of-the-art design tools, yet little has changed in terms of IC sales processes since the invention of the integrated circuit. By transitioning business processes such as device customization and sample procurement to the Web, the semiconductor industry will be able to reap the same benefits that successful e-tailers like Amazon, eBay, and Apple now enjoy.

Mass customization, improved customer service, and shorter delivery times are all unique benefits that can be realized by the transition to Web-customizable IC solutions. For an example of such a Web-based solution now in use, visit www.silabs.com/ClockBuilder. ■