Component Selection for Electronic product design - Page 1
Forum section: electronics / beginners

author: viji_rookie
author_rank: Contributor
timestamp: October 11, 2020, 03:07:56 pm
content: Component Selection for Electronic product designSummary:Any competitive industry or original equipment manufacturer (OEMs) products are required to have their equipment’s, materials and parts they design or procure are technology mature & with long lifecycle. And such product performance or solutions in turn generate revenue by product services either through AMCs or warranties offered. Selection and strategic sourcing of components is one of the most critical activities in the design cycle for any electronic system. The OEM parts, materials designed or procured could be an entire hardware system, subsystem or a components used in products.For most types of components, there are several choices from numerous vendors that could potentially be used. It is the responsibility of the component engineering group or design team to sift through these choices and choose the component that is just right for the design. Here let’s explore the various parameters to be considered for component selection, and sustenance or obsolescence processes available that designers could use for understanding and adopt for mitigating component risks and sourcing challenges.1. Parameters for Component SelectionThe parameters to be considered for component selection can be broadly classified as technical parameters and non-technical parameters. The selection process is, many a time, a tricky balance between the technical and non-technical aspects. The subsequent sections explain upon these parameters.1.1. Technical ParametersFunctionalityWhen choosing a material to manufacture a product functionality is vital. How well it does the intended functionality has to be considered as prime characteristic while choosing every component and devices in the product. Designers need to be aware of a whole range of user specification, functional and design requirements, material properties and so on. The first and foremost question to be asked by the designer is whether the component under consideration meets all the functions desired by the application. An example could be whether a certain power supply IC meets the voltage and current requirements of the application.DC Electrical CharacteristicsThe most important DC Electrical Characteristic of the device to be considered is the supply voltage(s) at which the device operates. Electrical parameters like voltage, current, power, accuracy, response time, speed, resolution, etc. are the core of the requirements, E.g. for a resistor, you need to see its resistance value, tolerance, temperature coefficient, wattage, etc. whereas its memory size, access time, data retention, endurance, supply voltage, and operating temperature for a Flash memory. In systems with multiple supply voltages, it is important to check the device’s input-output voltage tolerance to decide whether voltage translators are needed between the various components. The logic levels of the power supply input and output lines (VIH, VIL, VOH, VOL) decide how the component fits into overall system.Another example is, consider a DC-DC Converter IC, some of the electrical parameters would be input voltage range, output voltage accuracy, inbuilt protections available like over current, over voltage, under voltage cutoff, thermal shutdown, light load efficiency, power rating, thermal management, etc. Make sure you make a list so that you do not miss a critical parameter.AC Electrical CharacteristicsThe important AC Electrical Characteristics to be considered are the frequency of operation, rise time, fall time, propagation delay, setup and hold times. It is important to consider the minimum and maximum values of these parameters and not just the typical values. While interpreting the datasheet, it is important to note the conditions under which these parameters are measured.Power ConsumptionThe general guideline for this parameter is that it should be as low as possible. This becomes the decisive factor in choosing components for portable, battery operated systems. The designer could look at special features such as availability of sleep modes, idle modes etc. that enable to reduce the power consumption when the device is not active. For example, in a portable audio player, it would be ideal to choose a codec chip that not only has lower active power, but also supports switching to a low power mode when not playing back music.Physical SizeThe physical size of a component is another critical parameter for system design especially in the case of hand held and portable systems. Mechanical package, dimensions, weight, etc. plays a key role as well in part selection. With the smaller package, also comes the complexity of assembling, testing, and repairing. Example: if you are selecting an SMD resistor, it would very hard to manually solder a 0402 package vs. 0603 or 0805. Another example is the lead-less (BGA / LLP) packages. It will be complex from PCB design / manual soldering point of view, so carefully trade-off makes the best sense for overall requirement. In general, the goal should be keeping the overall weight of the product low as it directly impacts product bulkiness and shipping cost for a wearable product or for example a drone.Supporting Circuit ElementsWhile choosing a component, it is essential to consider the additional circuitry that allows the component to operate. With the levels of integration going ever higher, it would be better to choose components that support greater on-chip features so that the number of external components is reduced. Greater the on-chip features, lesser the cost, physical size and power consumption of the system. For example, when choosing a processor IC, the designer could look for the set of peripherals supported such as DMA Controllers, on chip memory etc. also in additional to the core processor function. When choosing Switched Mode Power Supply (SMPS) IC, the designer could look for ICs with built-in MOSFET. Another important factor to be considered is the number and type of power supplies required for the operation of the IC. For example, when choosing an Analog to Digital Converter (ADC), it would be essential to consider the Power Supply Rejection Ratio (PSRR) to decide on the ripple specification of the power supply that drives the ADC.Operating Environment Requirements and Reliability DataEvery component is specified to operate in a certain temperature and relative humidity, pressure, vibration grades. Based on this criterion, components are classified as belonging to the Commercial grade, Industrial grade and the Military grade. The designer could choose the appropriate grade component based on the system’s operating environment. And when it comes to Reliability - Comparison of component reliability parameters such as the Mean Time Between Failure (MTBF) of different components being considered would be essential for design of high reliability systems. While the MTBF data is not generally available from a component datasheet, this could be obtained from the manufacturer and used for overall system reliability predictions.Regulatory and Compliance requirementsRegulatory requirements of different national regulatory bodies place constraints on the choice of components. An example for this is the Restriction on the use of certain Hazardous Substances (RoHS) and Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) directives of the European Union. These directive bars the usage of Lead (Pb) and other hazardous substances in electrical-electronic systems and their potential impacts on both human health and the environment. Support for Pbfree soldering and compliance to RoHS directive could be an important criterion for choosing a certain component. Another example is to verify whether a module or subassembly like AC-DC Converter, being considered is certified to meet compliance of IEC, FCC, CE or UL requirements.IP, Development tools and ISE platformAvailability of quality Hardware development tools is a very critical parameter for design critical components such as Microprocessors, Microcontrollers, Programmable Logic Device CPLD or FPGA etc. Reference Designs, Software Tools of key suppliers like Altera, Xilinx, Intel and Microchip provides a lot of resources like industry-specific reference design, software tools to help designer evaluate the performance of the component as per product functional expectations or configurations before even designing anything. This heavily reduces the development time and chances of failure.And availability of Intellectual Property (IP) that can be licensed from the IC vendor or third parties is a critical choice that enables faster time-to market. For example, availability of different operating systems on a processor CPLD or FPGA, availability of audio or video codec software IP on Digital Signal Processor etc. enables the system to hit the market faster.Scope for EnhancementScope for future enhancement is an important factor since all requirements may not be clear enough upfront in the design phase. For example, choose memory packages that support larger capacity in the same footprint. Similarly, choose programmable logic devices that support larger number of logic gates in the same footprint.1.2. Non-Technical ParametersCostCost is a critical constraint in any component selection most of the time from sourcing standpoint. The important point to be seen is the cost of the total solution than just the cost of the particular component under consideration. For New product introductions (NPI), Proof of concepts (POCs) and new product under development (NPD) cost (or should cost) is the critical parameter for setting up the targeted price of the product for market. And in sustenance (legacy products) this cost information used for Values analyses and Value engineering (VAVE) activities.Multiple SourcesFor mass production, having multiple suppliers and manufacturers for the component is a desirable feature since it eases procurement and lowers cost due to competitive pricing by each suppliers . Also, the risk of component obsolescence is reduced. A good guideline to follow for selection of components like power management ICs (PMICs), buffers, logic gates, operational amplifiers etc., is to choose those packages that are made by multiple vendors.Stage of ProductionIt is essential to consider the stage of production the component being considered is in. For New product introductions (NPI), Proof of concepts (POCs) and new product under development (NPD), the component should be in the Early technology adoption phase or in Active Production phase and should be under mature state of its technology life cycle. Parts of Not-for-Future-Design (NFD) phase or obsolete phase should be avoided as much as possible. For components in early technology adoption phase, it is essential to verify if the production schedule of the component matches with that of the product being designed.LegacyComponents used in previous versions of the system are good candidates for a new version of the system. This permits reuse of device drivers, software, schematics, layout and knowledge, thereby reducing the risk. While reusing legacy components, it is important to verify whether the component is still in active production and also if there are any known issues with the component.2. Process for SelectionNow that we have seen the parameters for component selection, let us look at a good process for the selection. The first step is to understand broader priorities and business requirements like Technology of parts, methods of manufacturability, compliance and sourcing strategies. Classify the features as must-have and nice-to-have. This is followed by review or research to find the candidate components and detailed study of their datasheets. Some good resources for this research are internet search, literature search, IC vendor websites, competitor products, teardown reports, product roadmaps from suppliers and reviews. Once the candidate components are shortlisted, tabulate all the features of the candidate parts and review this with the concerned design teams. The review is important since system design has many stake holders such as the product designers, software developers, marketing teams and customers. If necessary, a more thorough evaluation can be done using evaluation boards from the IC vendor.The next step is to identify preferred and non-preferred sources for the component. A few points to remember in the selection process are summarized below. It is essential for the designer not to go by Sheet 1 of the datasheet, as many a time, this sheet highlights only the best aspects of the component. For each performance claim, note the conditions under which the performance is measured and verify if these conditions match the operating conditions of the system under design. The figures and graphs in a datasheet convey a lot of factual information, hence pay a lot of attention to these.Research for component selection is a continuous process and it is essential for the component engineering group to track the technology developments in semiconductor area of specialization and manage internal roadmap as strategic guidelines for internal product benchmarking. Such strategic teams should watch out for new component announcements and obsolescence notices (PCNs, PDNs) from IC vendor websites, newsletters etc. Independent reviews are also a good source of information. The study and research are best done well before the actual design cycle begins so as to cut down on the design time without compromising the selection process.3. Methodologies and Approaches to Component Obsolescence ManagementObsolescence management strategies of OEMs can be categorized within two distinct realms:I. ReactiveII. ProactiveA reactive approach to obsolescence management relies on taking action once a component event such as the release of a Product Discontinuance Notice (PDN) has already occurred, advising the OEM of an impending change in the component’s lifecycle. PDNs sourced through direct relationships with manufacturers, distributors, contract manufacturers and/or component procurement team then signal the OEM to react to the upcoming lifecycle change of the component.Whereas Proactive approach, however, focus on predicting component obsolescence prior to the issuance of the PDN. OEMs started to use a proactive approach to obsolescence management assign risk grades to each component and have appropriate measures in place to deal with the lifecycle change of a component in the future. Such an approach allows the OEM to predict lifecycle events long before a PDN is ever issued, allowing time to dedicate resources, find solutions and predict cost impact months or years in advance. Mitigating the effects of component obsolescence in an intelligent and proactive manner has become necessary in today’s dynamic electronic world. Reacting to obsolescence events that occur without prior knowledge is an added risk for the OEM which can add exorbitant costs and delays to the end product’s own lifecycle. Proactive approaches to obsolescence management using sourcing analytics and data points from independent sources, such as IHS Part analytics, Silicon Expert Technologies’ Parts Database, and few others allow OEMs to better manage risk and obsolescence in a sophisticated and well-planned manner. Though these webhosted databases has not complete set of parts category of limited part database, but solves the need of hour in lifecycle forecasting.Resources:http://www.eeherald.com/section/sourcing-database/indexhttps://www.ittiam.com/resource/component-selection-in-electronic-system-design/https://www.globalspec.com/productfinder/electronics_semiconductor_componentshttps://ekpower.se/en/complete-lifecycle-analysis-of-electronic-components-in-your-bom/About author:Vijay Vaikunthe has decade of electrical component experience from at GE and Visteon. He is currently supporting ILensys (Thermo Fisher Scientific) as Technical Lead - Component engineering group. Domain expert on Hardware PCB designing, Component Engineering, Strategic sourcing, Library development, DFA & DFM analysis, engineering support on fabrication and assembly process. He has successfully handled and implemented high performance hardware staff, product life-cycle processes and methodologies.Follow @https://www.linkedin.com/in/vijaykumar-vaikunthe/---------------------------------------------------------------- END ------------------------------------------------------------------