Triple LED controller for rear lamps

December 17, 2014 // By Christoph Hammerschmidt
The IC family E522.80 / 81 / 82 83 from Elmos AG is an LED controller device, designed for applications like automotive rear lights. The devices offer three channels each, with a maximum current of 140 mA. The channels can be switched in parallel to achieve currents up to 420 mA.

The E522.8x features comprehensive diagnosis functions that ensure reliable operation. For example, the devices monitor junction temperature and optionally external temperature and they detect over voltage as well as open and short circuit conditions. For LED clusters with more than three channels, a diagnosis interface is available. For failure handling the ICs offer two configurable operating modes: In Failure Feedback Mode the defective channel is deactivated and the individual failure is signalised to the system. Alternatively, the chips offer a Single Lamp Mode which means that all LED strings connected are regarded as a single light source. In this mode, all strings are deactivated if an error occurs. The IC then works on a reduced current, signalising the problem to the respective control unit.

A special feature is that the E522.8x enables designers to transfer the power dissipation in part to external shunts to achieve an even heat distribution without hot spots on the PCB. The dual circuitry topology avoids additional voltage drop at the linear regulator stage.

The LEDs can be dimmed individually by channel or as a whole. For dimming, a PWM scheme is implemented.

The devices are specified for an operating voltage range from 5 to 25V; maximum permitted voltage is 40V. The chips come in an SO16 package with exposed die pad. All 5222.8x versions are certified according to automotive specification AEC-Q100.

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