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Designing LED Driver Circuits For MR-16 Lamps With DMX-512 Interface | Cypress Semiconductor

Designing LED Driver Circuits For MR-16 Lamps With DMX-512 Interface

Last Updated: 
Jun 27, 2011

MR-16 fixture is a lighting industry standard format for small form factor lamps, and used extensively in retail lighting. They are well suited for a variety of applications that require directional lighting of low to medium intensity, such as track lighting, recessed ceiling lights, pendant fixtures, landscape lighting, retail display and bicycle headlights.
With the increasing need for energy efficient lighting, MR-16 lamps are using high brightness LEDs as illumination sources. There are LED packages available with multiple colored LEDs on the same die, allowing for MR-16 lamps capable of tunable white light or color light applications. Tunable white light systems allow the user to set the desired color temperature of white light, which can be very useful in retail lighting applications. These systems require an intelligent LED driver that provide the constant current power supply for the high brightness LEDs, modulate the intensity for color tuning and also provide a communication interface for control (such as DMX-512)

Figure 1. MR-16 Lamp & Fixture Internals


Cypress has developed a reference design for a compact LED driver solution, made to fit inside the MR-16 fixture, as shown in the figure above. The solution includes support for up to four channels of LEDs, such as in tunable white light systems. The driver board uses PowerPSoC for providing a constant current power supply for the LEDs and integrated intelligence for multi-channel LED control. The solution also integrates DMX512 communication, which provides flexibility to network multiple fixtures but maintaining individual control for each fixture.

The following table lists the specifications of the four-channel PowerPSoC solution. Figure 2 below shows pictures of the reference design board.

Table 1. PowerPSoC MR16 Fixture Controller Specifications



 Cypress Solution


 Number of LED Channels


 Number of LEDs/ Channel


 LED Drive Current

 700 mA per channel maximum


 Color Mix, Tunable White Light

 Communication Protocol

 DMX512-Physical Layer RS485

Figure 2. Fixture Controller Board


Complete design files for the reference design board shown above are available along with the application note AN56581. The design files include schematics, netlist, gerber files, BOM and sample firmware code examples.