I2C LED Driver

I2C LED Driver is a high power LED driver with i2c control and 12bit resolution.

Features

• High maximum current

  I2C LED Driver uses the National Semiconductor LM3409/HV chip, which allows for up to 5A LED current using the appropriate external power mosfet and components.

• High maximum voltage

  I2C LED Driver can be configured with the LM3409 for 6V to 42V input voltage or the LM3409HV for 6V to 75V input voltage

• i2c analog dimming

  I2C LED Driver's i2c bus is handled by the MCP4725 12Bit Digital-to-Analog Converter. The MCP4706 and MCP4716 DACs are drop in replacements for 8 and 10 bit resolution, respectively.

• PWM dimming (depricated)

  I2C LED Driver v0.5 and before can be used for simple PWM dimming. This feature is no longer supported with v0.6 due to the simpler and superior i2c method.

• Direct analog dimming (depricated)

  I2C LED Driver v0.5 can be used if direct analog dimming is prefered. This feature is no longer supported. See i2c analog dimming.

Programming

• Communication via i2c bus

  Communication is done with 4 bytes:

  • 1 byte - address
  • 2 byte - commands
  • 3 and 4 byte - registers of the 12 bits (last 4 bits are ignored)

• Addressing

  The 7 bit address is composed of 1100 for first 4 bits + 3 additional bits via configurable pins. On the MCP4725, you have 4 options when you order 110000X, 110001X 110010X and 110011X where X is set to either 0 or 1 via the external smd jumper.

  Refer to the datasheet for more information.

  A library will be made available in the near future.

Hardware

• CAD software

  The board and schematic are being developed using the the free version of Eagle PCB. set to either 0 or 1 via the external smd jumper.

• Limitations

  Since only 3 bits of the address on the MCP4725 are configurable, that means only 8 driver boards can sit on a i2c bus at one given time. If more than 8 driver boards are required a simple solution like using the MAX4562 for up to 3 more sets of 8 boards, or the MAX4572 for up to 7 more sets of 8 boards can be used.

  More about this setup can be read in the Maxim App Note 955.

Getting a I2C LED Driver

• PCB

  There are plenty fab house in China that offer PCB services for very reasonable price. Seeed Studio will make 10 boards for a little over $10. iTead Studio has very similar offer.

• Power Supply

  I2C LED Driver is a switch mode regulator based buck driver that is a little more forgivin in the amount of input voltage it can handle, compared to the LED dropout voltage, however try to keep the total forward voltage of the LEDs not more than 10V under the input voltage. The closer the less work the regulator has to do.

• Bill Of Materials

  The BOM files are for 1A, 48V input setup. It is highly recommended that you go throgh the component selection part of the datasheet to ensure that you have selected the appropriate components for your setup. Mouser project for the 1A, 48V setup can be found here.

License

Licensed under the TAPR Open Hardware License (www.tapr.org/OHL)