Digital Optocouplers Deliver Low Power Consumption And High Isolation For Automotive Applications White Paper

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As automotive systems employ ever-increasing amounts of electronic and electrical components, the systems become more susceptible to transients and short circuits, additional protection must be included to prevent critical systems from damage. This becomes especially critical when an electric motor provides the drive for a hybrid or all-electric vehicle. In such cases, high voltages of up to hundreds of volts can be introduced into the powertrain system. Additionally, beside high-voltage power conversion, data communications subsystems such as Control Area Network networks must be protected so the high-voltages do not feed through to other subsystems such as the Engine Control Unit, Battery Management System, Climate Control System, etc. Some sample interface circuit diagrams illustrating how the optocouplers are employed in the applications are included.

High Reliability

LEDs have benefited from over 35 years of improvement and refined manufacturing processes. Avago leverages that experience to deliver highly-reliable LED optocouplers that serve many markets --industrial, military and space applications to name a few. Key to the reliability is the LED fabrication technology developed by Avago that achieves automotive AEC Q100 grade performance.

Avago optocouplers are stress tested at 150 °C and a LED drive current of 20 mA. The parameter of current transfer ratio is proportional to LED light output. A CTR vs Time chart indirectly measures LED degradation over lifetime. As shown in the graph, there is almost no degradation after 5000 hours of stress testing. Projections based on this measurement extrapolate to a lifetime of more than 100 years of operation in automotive applications.

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