and high-performance analogue ICs that form the core of Linear Technology’s (now part of Analog Devices) products that a skills gap is growing. It is easy to look at a system with huge FPGAs and think about the challenges in digital terms while overlooking the difficulty of powering the parts. Sub one-volt cores, consuming 10-20Amps require good transient response of <50mV over all conditions making loop response, layout, voltage reference accuracy and load monitoring critical. Add in higher PCB densities, increased clock speeds, concerns over conducted emissions and operating temperature considerations and these quickly become analogue and RF problems. The number of designers specialising in these areas has diminished while the need for high-performance solutions is on the increase, hence the skills gap. A good supplier will address this with applications support, evaluation boards, circuit analysis models and, of course, with great products. One approach that helps


address the skills gap, performance requirements and long term availability of products is the increasing use of module technology. Linear Technology’s range of µModule voltage regulators and signal chains resemble a surface mount IC, each product includes complete system-in-a-package solution that simplifies design and minimises external components. Sub-families of parts can be created with compatible footprints and pinouts making it easier to scale up or down the power or performance requirements without major changes to the circuit board layout. Internally, multiple IC dies of different technologies are combined with passive components on a substrate which is over moulded. The layout and design are carefully optimised for electrical performance and thermal efficiency and will achieve a smaller solution size than is possible with standard component packaging. Built to the industry’s highest standards, these modules offer outstanding reliability approaching that of standard ICs.


Commercial considerations Another factor in the selection of components at the design stage, is that of cost. First, it is important to distinguish between component price and solution cost. Using the example of the µModule voltage regulator above, the solution cost equates to the unit price, whereas looking only at the DC-DC controller and MOSFET unit costs would not take in to account the passive components, magnetics, design time and technical challenges associated with developing a high- efficiency switching regulator. Again the skills gap may play in to this calculation. Furthermore the lifetime cost for a given solution will be heavily dependent on the long-term availability of the component. If a redesign is required the costs could easily dominate the lifetime cost as the example below shows. Component 1 has to be redesigned twice whereas component 2 remains available for the lifetime of the programme.


www.cieonline.co.uk


a more informed choice for new designs. It is therefore important to dedicate time to cultivate such relationships.


Table 1.


The risks of reworked & counterfeit components The Semiconductor Industry Association estimates that counterfeit parts cost U.S. semiconductor companies more than $7.5 billion per year in lost revenue. There are many examples of counterfeit parts being found in the aerospace and defence supply chain and the consequent danger of equipment failure with potential for injury or loss of life. A quick search of YouTube finds numerous examples of component salvage operations and sales outlets for what amounts to scrap or misrepresented components. While efforts are being made to tighten up on illegal activities, the simple solution is not to buy from unauthorised sources or brokers. It is also important to ensure that such procurement policies are extended to Contract Manufacturers and that they are not permitted to mix inventories of common parts purchased for other customers where controls and procurement policies may differ. Careful selection of suppliers and a close working partnership will also assist in solving the most intractable obsolescence issues. Linear Technology will, under strict conditions, offer components in die form to enable customers to engage third party packaging where the original package piece parts are obsolete. From a design perspective, this can be a helpful option where no other changes or PCB redesign is required.


Clearly, even a reduced unit price with


each redesign is insufficient to offset the redesign costs, which may be far more substantial than those indicated here in reality, particularly for more complex components with software implications.


Designing around component obsolescence


When selecting components for a new design good component engineering specialists can give a vital perspective on the track record of suppliers from their experience, but this is not simply a


question of looking in the numerous on- line, commercially available parts databases. Frequently these have been shown to give mathematical predictions of impending obsolescence that fail to take into account individual manufacturer policies. For example, at Linear Technology, we have a non-obsolescence policy and we still offer for sale products released three decades ago such as the LT1001. A close supplier relationship will bring with it access to inside information on component popularity, manufacturability and new process technologies that assist in making


Conclusions Design managers are major stakeholders in the supplier selection and development process and should encourage designers to develop close working relationships in pursuit of their design goals. Strong innovation, stability of supply, high quality and a track record of long-term commitment to the Aerospace and Defence market are all elements that form the basis of dependable supplier relationships. Component selection is not just a matter of finding a part that fits the performance need. First-class design support from the supplier will reduce time to market, assist in bridging any skills gaps and facilitate informed choices in terms of component selection. This will deliver the most competitive solution and reduce the longer-term risk of obsolescence problems. Beware of misinformation, the Internet is full of instant answers and data but the knowledge and experience of component specialists and good contacts at suppliers will serve higher quality information.


www.linear.com Linear Technology (UK) Ltd (now part of Analog Devices) Tel: 01628 477066


Components in Electronics July/August 2017 9


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