Rumours about Würth planning a play in the intelligent LED market have percolated the industry for almost a year. Driving large numbers of light-emitting diodes is an interesting task though. Books like The Art of Electronics provide ample documentation for exotic modulation schemes, such as Charlieplexing. Smart LEDs break this pattern by combining an RGB LED with a controller IC. This means the individual LEDs can be cascaded in the fashion shown in the two figures. Figure one was kindly provided by https://www.richis-lab.de/Opto06.htm and is used here with permission.

Data communication requires but one GPIO pin; the wide use of the components ensures that driver libraries are available for all commonly used microcontroller architectures. Circuit integration could not be more straightforward – it is recommended to place one capacitor near each LED for optimal performance.

Advanced form factors provide versatility to designers

Given that the integrated circuits used in smart LED products are standardised, manufacturers are free to innovate by providing form factors that make physical integration easier. Würth Elektronik’s smart LED portfolio consists of four different products, shown in an overview in the table.

The 1315050930002 is an embodiment of the standard variant. Thanks to standardisation, this part can easily be substituted, thereby simplifying the bill of materials. Interestingly, Würth Elektronik decided to use diffused plastic for the lens. This unique and strategic choice makes the colour appearance "smoother" and hides the integrated circuit from view – the figure shows the Würth Elektronik part next to a third-party product found on a LED strip.

Würth also enters the waterproof LED market with the 1312121320437. According to the datasheet, this part boasts an IP rating of IPx7, which greatly simplifies its use in challenging environments such as the humidity found in boats or other water sports applications. 

Furthermore, the 1312020030000 variant of the chip is significantly smaller, which yields significant space savings on the printed circuit board.

The 1313210530000 is an embodiment of the side-view LED, a specific type of light-emitting diode whose radiation pattern ensures that colours are visible from the side. The radiation diagrams contained in the datasheet provide further information about this.

Due to the standardisation of the driver chips used in smart LEDs, documentation for their use is commonly available. Furthermore, best practices related to PCB layout, capacitor placement, and other aspects apply independently of the product variant.

Generating the control waveforms is usually done via a hardware accelerator. In the case of the ESP32, SPI-like peripheral devices are commonly used to ensure timing stability and freedom from jitter. The PIO is usually used on the Raspberry Pi Pico to generate the waveforms. Adafruit provides an excellent example at https://learn.adafruit.com/intro-to-rp2040-pio-with-circuitpython/using-pio-to-drive-a-neopixel, which uses the following state machine code to achieve highly stable pixel timings:

 
  program = """
.program ws2812
.side_set 1
.wrap_target
bitloop:
   out x 1        side 0 [6]; Drive low. Side-set still takes place before instruction stalls.
   jmp !x do_zero side 1 [3]; Branch on the bit we shifted out previous delay. Drive high.
 do_one:
   jmp  bitloop   side 1 [4]; Continue driving high, for a one (long pulse)
 do_zero:
   nop            side 0 [4]; Or drive low, for a zero (short pulse)
.wrap
"""

In practice, Würth’s application note "ANO009 | Understanding parameters in ICLED datasheets" deserves additional praise. Not only does it provide a detailed discussion of the various parameters found in the datasheet, but Würth Elektronik also provides a reference section with a vast array of literature permitting developers to study the task more deeply.

Finally, the datasheets of the individual components must also be studied to discover more about limits and ideal operating points. The WL-ICLED family expands Würth Elektroniks' (already excellent) portfolio into the realm of smart light-emitting diodes. This is valuable not only in itself but can also simplify the bill of materials. Finally, smart form factors such as the water-resistant variant and the side-view version provide flexibility in the placement of the optical components. This is highly helpful when working on fashion or marine applications.