By Bob Scannell
Analog Devices Inc. Multichip Products Group
For some, commercial-off-the-shelf (COTS) has been a means to faster time-to-market and lower costs. For others, it has meant a compromise in performance and/or reliability. It is not too often that one reads of a COTS application without some concern of compromise.
With the exception of custom circuit developments, most integrated circuits applied to military systems, past or present, have carried some implied compromise. A military part has typically been an IC developed for some unrelated market-segment, and then transferred into a ceramic, hermetic package for the military.
The point is that an IC developed for the communications industry does not necessarily match all of the intricate requirements of a missile seeker program. Why not look for a new paradigm which applies appropriate technology to directly serve all of the needs of a particular military/aerospace market - high performance, high reliability, high density, long-life, off-the-shelf, and low cost?
In examining the basic requirements behind military and aerospace applications such missiles and satellites, for instance, it is clear that these applications have been and remain among the most challenging - commercial or military. These are extremely complex systems that require continuing innovation in electronic component design and technology.
Yet due to enticing volumes and growth projections in other markets, few component designers in the semiconductor industry are directly working on challenging military/ aerospace needs. So, the question is, will military and aerospace contractors ever get exactly what they want from a semiconductor company`s component databook?
In light of this changing environment, leaders of the Multichip Products Group (MCP) of Analog Devices Inc. in Greensboro, N.C., have taken a renewed look at their approach to serving this market. The result is a multichip product strategy that takes advantage of the company`s unique position within a leading semiconductor company and successfully applies a proven design and technology base directly to the "new" military/aerospace customer.
Multichip module (MCM) technology has long been associated primarily with high density, and relatively few companies have leveraged the high-performance aspects of this technology. In addition, the high-reliability nature of MCMs is often overlooked, and few designers ever associate MCMs with low cost.
Nevertheless, the fact is that the most undervalued benefit of an MCM is its ability to free a component designer from the burden of typical performance-limiting single-chip packages. A single-chip IC package is often developed as an afterthought and is primarily viewed as a means to transfer signals to a printed circuit board and protect the IC.
An MCM package on the other hand, is an extension of the components within it, and optimizes the electrical and mechanical properties of its total functionality. With embedded and optimized signal interconnect and short, low-inductance signal paths, MCMs can have significantly better die performance than single-chip packages and standard printed circuit board designs. This, of course, requires looking at MCMs as more than a package-subcontracting effort, and instead emphasizes design optimization based on high-speed, mixed-signal chip integration technology.
A typical missile development program today is a platform upgrade, whereby engineers enhance capability and features by orders-of-magnitude within an existing missile body. The overall missile system encompasses very complex and diverse subsystems including seeker, guidance, control, power, propulsion, armament, and airframes. Expanded mission complexities are requiring multiple seekers, improved accuracy, advanced electronic countermeasures, and other improvements while still requiring minimum weight, volume, and the highest of reliability.
Time-to-market and cost-reduction pressure are forcing contractors to look to standard databooks for component solutions. Yet fewer and fewer suppliers are paying any attention to this market need. Furthermore, the complexity of requirements is unique, so system optimization is difficult unless systems designers develop components specifically for the application. That is not to say custom parts, but rather off-the-shelf components developed specifically for the missile signal chain.
Often these components can apply to other military and aerospace applications as well. Satellites, ruggedized communications, and radar platforms tend to share commonality in certain subsystem specifications. And importantly, they share the need for high performance/density and high-reliability.
An MCM design, by nature, closely links and optimizes the three design criteria of critical importance to modern applications: electrical specifications, mechanical specifications, and environmental specifications. By leveraging existing silicon, the design effort now focuses on the interconnect and the package. This is the key to each of these three variables because the package limits a chip`s performance more than anything else does.
The job of a missile system designer is made more difficult from the start when he works with standard single-chip packages because typically the die has already been "compromised" in at least one of the above areas. However, the designer can optimize his system by developing a multichip product, starting with the bare uncompromised die, where electrical/mechanical/environmental specifications together drive the design from the early stages. System verification, test, and qualification can also be simplified since modules or sub-systems are fully tested and characterized by the manufacturer.
It is one thing to have a "device" which meets system requirements, and yet a completely different matter to have a "product" which meets program requirements. Military customers and programs have different needs from their commercial counterparts. These differing needs include:
- system complexity that requires flexibility during design, and extensive trade-off studies;
- increased emphasis on thermal/ mechanical system design due to complex and extreme environments;
- lengthy and detailed development cycles; and
- long-life production.
Recognizing this, as part of re-focusing on the military-COTS customer, leaders of the Analog Devices MCP group have established operating principles and design disciplines markedly different from those followed by standard IC development groups. Military thermal/mechanical environments typically are among the most severe, and this requires extensive design, analysis, and optimization efforts.
To meet this need, our standard MCM datasheets carry significant additional detail in this regard, as well as informative modeling/analysis results. Furthermore, Analog Devices officials make available engineering support and additional data as necessary for continued customer evaluation.
Major military/aerospace developments encompass multiple contractors and require significant government reporting/involvement. The entire supply chain for these systems needs to be sensitive to these needs and capable of supporting tasks such as analysis, tradeoffs, and lobbying. The Corporation as a whole has made a clear commitment to the military/aerospace market and the COTS initiative. This applies not only to the Multichip solutions approach, but to more than 6,200 standard-product COTS ICs in the Analog Devices databook - a mix of space, military, industrial, and commercial grade, as well as a QML program.
By developing components specifically for military/aerospace signal chains, Analog Devices officials address the product longevity issue as well; Parts are developed as long-term products with 15- to 20-year lifespans, specifically for a known long-life market.
Industry initiatives such as the Affordable Multi-Missile Manufacturing Program aim to improve missile development cycle time and cost, while maintaining performance and reliability standards. This is exactly the goal of the Analog Devices MCM/COTS synergism.
As for cost, while designers typically associate MCMs with high cost, this has been primarily driven by the price structures of known-good-die and third-party silicon. By leveraging a broad portfolio of in-house mixed signal silicon, Analog Devices has developed many MCM solutions that contain 100 percent in-house silicon. This has enabled engineers to design MCM solutions with a fractional delta in cost over the component silicon. This delta is small enough so in system level cost savings achieved with the MCM can more than make up for it. Benefits include fewer boards, less complex boards, fewer enclosures and connectors, and easier assembly and test.
Finally, it is important to contrast the Analog Devices MCM approach with standard high-density printed circuit board development as its involves the relationship between an OEM design-team and a contract manufacturer. The business model enables the customer to:
- leverage a high percentage of in-house silicon, which enables designers to test subsystems even more extensively than individual ICs;
- get involved in the military/aerospace market that drives standard product roadmaps and technology development;
- achieve significant performance improvements from lower inductance signal paths and low impedance routing;
- pursue technology-driven design, rather than force a design into a technology;
- typically save board area by 50 to 90 percent; and
- support product and applications that are focused on the military/aerospace market.
With a cost-competitive MCM technology well matched to the new military/aerospace COTS requirements, leaders of the Analog Devices MCP group have formalized a business charter focused on developing components specifically for this market.
This unconventional approach shall actually promote increased interaction between the military customer/supplier, while still supporting the improved time-to-market and cost reduction goals. The military/ aerospace customer needs will directly drive standard product development from the initial stages, resulting in COTS components - without any compromise.
Bob Scannell is a Strategic Marketing Manager for the Analog Devices Inc. Multichip Products Group, in Greensboro, N.C. He has been with Analog Devices since 1995. Previously he worked for Rockwell International`s Tactical Systems Division in the area of advanced digital signal processing architectures and multichip packaging. Those interested can contact him by phone at 910-605-4031, or by e-mail at [email protected].
