The ZVN4206AV is considered to be the ideal automotive relay driver. It allows significant simplification and cost reductions to be made when replacing standard drivers such as bipolar Darlington transistors. The following note explains the popularity of relays as high current switches in automobiles, some of the problems to be solved in designing driver circuits, a standard driver circuit and an improved ZVN4206AV based circuit. The excellent performance of the ZVN4206AV is demonstrated and circuit options discussed.

The introduction of the ZVN4206AV provides a far simpler, if not the simplest possible solution to the problems of relay drivers. It is an avalanche rated 60V 1W N-channel MOSFET designed
specifically for use with automotive relays. The ZVN4206AV can drive relays with coil currents up to 600mA, and doesn’t require a catch-diode to clip the turn-off transient caused as the relay is
deactivated. The energy stored in the relay’s magnetic field is dissipated harmlessly by avalanche breakdown of the ZVN4206AV’s body diode. The same body diode also protects the MOSFET in the event of reverse battery connection. Characterised for 5V gate drive it can be driven directly from standard logic with no interface components.

Read more: http://www.zetex.com/3.0/appnotes/apps/an10.pdf

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