Automotive Designs Accelerate Demand For Passive Components

Space-Saving Suppressors
In addition to MLVs, other space-reducing alternatives are being called on to perform EMI suppression. One of them is the capacitive technology pioneered by X2Y Attenuators LLC.⁵ Its multilayer capacitor structure, which was introduced last year, achieves very low values of ESR and ESL, so that it's possible to implement single-component broadband EMI filtering for dc motors.

Furthermore, given that as many as 100 motors are currently in a typical luxury vehicle, the need for simple low-cost filters is already significant and should only increase in the future. Aside from just motors, many other applications for EMI filtering exist throughout the vehicle. Hall Effect, ABS, and other sensor applications, which typically have power, ground, and signal lines coming off the sensor, also require broadband filtering.

As an example of the technology's promise, consider test results obtained when a single-component X2Y filter was used to suppress the EMI from a 12-V dc motor (Fig. 3b). The 1410-size chip attenuated the motor's radiated emissions over the 150-kHz to 1000-MHz frequency range by 25 to 50 dB, pushing EMI down almost into the noise.⁶ In doing so, the single-component filter outperformed more traditional filters that were built with up to seven components.

Such technology also is attractive in automotive applications because its failure mechanisms meet automotive requirements for reliability. If bombarded with excessive RF, the device may go open circuit. "More than likely, this is the only failure," claims Tony Anthony of X2Y. According to X2Y, the motor filter chip can handle 1.5 to 2 A of RF with no limit on dc current because the device operates in bypass. In addition, the device's performance doesn't degrade over the typical automotive temperature range.

Initially, this technology was only produced in a ceramic dielectric with breakdown voltages of up to about 100 V. But development of X2Y designs in other dielectrics like film, which boosts breakdown voltage ratings of up to 600 V (and with still lower ESR), could expand the technology into the area of bulk capacitance.

That raises the possibility that X2Y-type capacitors could replace electrolytic and ceramic styles. Such a development could be applicable to automotive designs, as would the use of MOV dielectric materials to build single-component solutions for transient suppression and broadband filtering (as with the MLVs from AVX).

Beyond the filtering and transient-suppression applications discussed here, numerous other opportunities exist for passive components in future automotive designs. Passives might not be the key enabling technologies in most cases, but they will undoubtedly affect the performance, reliability, and cost of many new electronic features.

References:

1. "Ceramic Solutions For Automotive," DuPont Microcircuit Materials, www.dupont.com/mcm/cerautomotive.html.
2. For a look ahead at the rising electronic content planned for future automobiles, see diagrams of General Motors' Precept, a PNGV hybrid-electric concept vehicle. The Precept contains complex networking structures to support a host of electromechanical devices. Further information is available in "Low Power Flexible Controls Architecture for General Motors Partnership for a New Generation (PNGV) Precept Vehicle," by Joe LoGrasso and Kevin Kidston, General Motors Corp. and Walton Fehr, Motorola Inc., Convergence 2000 proceedings, paper number 2000-01-C060, p. 395-409.
3. "Power Electronics And Electric Machinery Innovations-U.S. Government's Role in PNGV," by Donald J. Adams, Oak Ridge National Laboratory, Convergence 2000 proceedings, paper number 2000-01-C063, p. 427-435.
4. "Multilayer Varistors In Automobile Mux Bus Applications," by Ron Demcko, AVX Advanced Products Group, SAE International Congress and Exposition, Feb. 23-26, 1998, paper number 981106.
5. "Capacitive Technology Performs Filtering And Decoupling With Fewer Parts," Electronic Design, Feb. 7, 2000, p. 25-26.
6. "Broadband Testing Of Low Cost Filter Solutions For DC Motors," by James P. Muccioli, Anthony A. Anthony, and others; Interference Technology Engineer's Master (ITEM) Update 2000.