Murata offers ceramics for vehicle electronics

  • 16-Nov-2008 01:54 EST
Murata EVC2.JPG
Murata developed a proprietary ceramic material that claims both large capacitance under dc bias and high allowable ripple current.

“Ceramic-based electronic components offer either a downsizing path or less cost over traditional materials, depending on the application,” said Peter Tiller, Senior Group Product Manager for Murata. He believes ceramics offer incremental reliability and robustness over traditional materials.

One example of downsizing is the EVC series of monolithic ceramic capacitors, designed for power electronics. The company touts the series as delivering higher permissive ripple current capabilities, high voltage, and large capacitance—­in a smaller package.

“Film-type capacitors generate more heat than ceramics. Using ceramics allows us to build smaller capacitors, enabling downsizing those devices needing capacitors,” explained Yuji Nakanishi, Automotive Marketing Manager for Murata.

Smaller capacitors that operate at higher temperatures are critical in the design of hybrids and electric vehicle motors, according to Murata. Murata believes its EVC ceramic capacitors deliver lower equivalent series resistance and equivalent series inductance compared to equivalent film and electrolytic capacitors.The maximum rated capacitance is 630 V dc with a capacitance of 12 microfarads at 400 V dc.

Other examples of Murata extending its product line for vehicle applications are additions in ceramic-based thermistors for sensing temperature. These new products are both positive and negative temperature coefficient (PTC and NTC) types.

­“Our PRF PTC sensor is really a go/no-go sensor for detecting overheating,” explained Tiller. The NCP series of NTC thermistors are aimed at measuring temperature accurately. First developed for consumer electronics, the technology was extended by Murata for automotive applications by designing the NCP series to meet the required ELV/UL and AEC-Q200 standards. Both automotive-grade NCP and PRF sensors are surface-mount and operate in temperatures from -40ºC to +150ºC (-40ºF to +302ºF).

Designed primarily for over-current protection, Murata’s PRG21/18 PTC thermistors should be used where small packaging and high reliability are needed. A ceramic multilayer PTC thermistor, it meets ELV/UL and AEC-Q200 standards.

“These PRF thermistors can be used with LEDs to control current dynamically, replacing ICs or resistors now used. They could also provide over-current protection for hybrid batteries or with car radios. With no hysterisis, they act as resettable fuses,” explained Tiller. He goes on to say that while polymers are useful in detecting higher currents, ceramics offer lower cost and more robust operation in low-current applications. He describes low current as less than six amps.

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