Saving Money with Programmable LEDs

Do you use multiple decorative LEDs in your product? Are you interested in saving money and board space by moving to programmable LEDs, but don’t know where to start? Here is a short primer on the differences between the two types of LEDs, and how to get started with them.

Non-programmable LEDs have been the staple of decorative illumination in consumer electronics for many years. They are available in several different types such as axial-lead through hole, and surface mount. They are available in several standard colors such as green, red, amber, blue, white, and some in custom hues. Once they are placed on the board, however, their color output will always remain the same; only the luminosity (intensity) can be changed by driving them with more or less current. Additionally, most micro-processors used in consumer products have limited output drive strengths, so LEDs are typically driven with an dedicated transistor or LED driver chip. In the case of RGB LEDs, each die must be driven from a separate driver, meaning three discrete driver chips are needed, along with decode logic and flip-flops to latch state. This combination of costs can start to add up.

simple transistor drive of a single LED

The programmable LED typically has three or more LED die inside each package, and they have an LED driver chip inside each package. The driver chip handles all the interaction with the microprocessor, it drives the LED die directly without any intervening logic, and it contains an output driver that will source a 25ma drive signal in order to daisy chain data to the next LED. Even more than discrete LEDs, the programmable RGB can display multiple mixes of color that result in every hue imaginable.

driver die bonded out to three led dies

The programmable LED thus replaces all on-board logic devices, transistors, and even most passives, requiring on a local decoupling capacitor and possibly a series termination resistor on the drive signal from the microprocessor. The resultant cost is much lower on “per LED” basis. Want to get exact numbers? Please contact us and let us show you how!

 

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