VIEWFROMTHE TOP Murata headquarters
Don’t unDerestimate the powerof passives
Without products such as capacitors, advanced devices such asmicroprocessors wouldn't function properly By Kiminori Yamauchi,Murata
Passive components – resistors, capacitors and inductors – had often been consideredminor players in the electronicsworld. Until recently, their semiconductor counterparts had continually overshadowed them. As themarket has evolved, so too has the perception of capacitors, particularly those of themonolithic ceramic variety. Without them, advanced devices such asmicroprocessors, digital signal processors,microcomputers and field-programmable gate arrays,would not be able to function properly.
Also, it is becomingmore apparent that buyers increasingly
understand the vital role and complexity of passive components and recognize the added value of passives whichmake use of the latest in component developments.
Capacitors have proven theirworth countless times in terms of
supporting power supply requirements, eliminating unwanted noise andmitigating performance degradation. Now, the size of the monolithic ceramic capacitormarket is the largest among all of the other capmarkets – namely aluminum, tantalumand film.
This acceptancewas hard fought. Monolithic capacitorswere first
introduced in the early 1960s. At that point, itwas a 100-pFmodel targeting LC resonant circuits in AMradios and consisted of 50-μm dielectric filmlayers. The history since then can best be described as size reduction coupledwith capacitance enhancement.
Murata used titaniumoxide as the dielectricmaterial during this
initial stage, but introduced bariumtitanate shortly thereafter. Following that, the relative dielectric constant has been continuously increasing as a result of improvementsmade to thematerial. To date, that value has reached approximately 3,000 and represents twice the order ofmagnitude over titaniumoxide’s constant.
Over the course of the last five decades, the semiconductor
market has changed dramatically and that is reflective formonolithic ceramic capacitors as well. Now, decoupling applications account for 70% of the demand. Asmentioned above, these capacitors are arranged aroundmicroprocessors, DSPs,microcomputers, FPGA’s or other semiconductor devices to support proper operation. The number of passive components used in these devices is enormous. For example, approximately 730 units are in a typical notebook, 230 can be found in amobile phone and digital TVs and car navigation systems both use around 1,000.
4 | September 2010 In these roles, they have twomain functions. First, theymust
support the semiconductor’s power supply,which can have varying current demands. Second is the elimination of noise – specifically electromagnetic interference. Generally, capacitors featuring the former function are considered decoupling and thosewith the latter are bypass. Now, both functions can be fulfilled at the same time because of high-capacitancemonolithic ceramic caps.
The secondmost notable application after these is smoothing
filters arranged at the output of DC-DC converters. While this is something that aluminumand tantalumhad a leg up on,monolithic ceramic capacitors havemade great strides over the last 10 years in reducing the size and thickness of electronic devices. Thiswas largely driven by semiconductormanufacturers.
In addition to serving as a smoothing filter, the cap also constitutes
part of the feedback loop of a DC-DC converter. For example, if the equivalent series resistance (ESR) is too low, the phasemargin also decreases. This results in the converter not operating in a stable manner. Simultaneously, electronicsmanufacturers have increased demands for smaller and thinner DC-DC converters. Tomeet this need, power semiconductor devicemanufacturesmade it possible to usemonolithic ceramic capacitors by improving the control circuit in DC-DC converter ICs. Around 2000, thesemanufacturers began selling the newICs, further demonstrating thatmonolithic capacitors are an integral part of the circuit.
Somoving forward, how domonolithic ceramic capacitors evolve
beyond size and thickness reduction? With almost 50 years under its belt,Murata is looking at continuing developing the capacitor with electrical characteristics and reliability-related properties that are optimized for specific applications – like the hybrid and electric automotivemarket. On this point, the company is developing commercialized products with a higher noise absorption effect by reducing the equivalent series inductance value and by controlling the equivalent series resistance value.
Kiminori Yamauchi is executive vice president and director of the Component Division ofMurataManufacturing in Japan
www.murata.com www.electronics-sourcing.com
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