Solutions for Common LED Design Errors in Segmented Display and Multi-Indicator Applications - App Note

LED displays and individual lamps are commonly used as information or status indication devices. These products are typically categorized as intelligent or non-intelligent. An intelligent LED display is one that has an on-board IC integrated with the LEDs, where all the electro-optical biasing of the discrete LEDs has already been provided to the end user. The user varies the brightness of the LEDs by simply changing a combination of "1s" and "0s" in the control register of the IC. The active semiconductor chips have already been matched by the OEM and thus uniformity is provided. However, a non-intelligent display or individual lamp is made up of a semiconductor chip(s), contact wires, and some packaging to provide mechanical stability, environmental protection, and optical lensing. These products are seven and sixteen segment displays, light bars, and discrete lamps. These non-intelligent devices require the designer to determine the electro-optical biasing configuration to achieve a desired brightness and uniformity. The intent of this literature is to address two of the most commonly found biasing errors of non-intelligent LED devices and provide solutions that will allow the designer to avoid these errors in the pursuit of an optimum LED design.