November 2010

Multilayer varistors

Matched-pair array protects FlexRay from ESD and EMI

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TDK-EPC, a group company of the TDK Corporation, presents a new matched-pair array from EPCOS that combines ESD protection and EMI suppression in a single multilayer component. The increased protection requirements of FlexRay bus lines in particular can be reliably met with this space-saving matched-pair array of the B72812* series.

As FlexRay offers a higher data rate, by up to a factor of 20, than the CAN, almost entirely uncorrupted transmission can be assured. The unshielded twisted lines used represent an additional challenge to the interference emissions and interference immunity of this bus system. The good EMI suppression is assumed by the closely matched narrow-tolerance capacitance values (<3 percent) of two capacitors (100 pF) connected in parallel and inte-grated in the array. In addition, the low parasitic inductance of the component assures good attenuation in the high frequency ranges.

In addition to the increased EMC requirements for FlexRay, the new matched pair also assures the ESD protection of sensitive downstream semiconductors.

The matched-pair array in the 0508 case size moreover protects against load-dump pulses (up to 27 V/0.3 s) and jump-start pulses (up to 28 V/60 s). Prototypes of the new component are now available.

Glossary

  • FlexRay: A field bus system designed to satisfy the increased networking requirements of future motor vehicles. It focuses mainly on the higher data rate, real-time capability and reliability required by the growing number of driver assistance systems in the drives and chassis of cars. The FlexRay standard is currently being adopted in an ISO standard.

Main applications

  • FlexRay bus lines in automotive electronics

Main features and benefits

  • Combined ESD suppression and EMI protection in a single component
    (one component instead of four)
  • High signal integrity thanks to narrow-tolerance capacitance matching of <3 percent

Key data

SeriesB72812
Case size 0805, matched-pair array
Operating voltage [V DC]16
Varistor voltage at 1 mA [V]27

Max. clamping voltage at 1 A,

8/20 µs [V]

66
Capacitance [pF]100
Capacitance matching [%]<3
Load dump27 V/ 0.3 s
Jump start 28 V/ 60 s
EMC requirements of FlexRay Physical Layer EMC Measurement Specification FlexRay,
version 1.0; IEC 62132 parts 1 and 4
Contact discharge ESD capability ISO 10605, IEC 61000-4-2 level 4
(8 kV contact discharge, 15 kV air discharge)

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