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LM3435: LED current of register is meaning IL_avg or IL_max

Hardy Xue
Expert 3640 points
Part Number: LM3435

Hi Team,

We can setting LED current level by register 0x00H ~ 0x03H. Does the LED current register setting for IL_max or IL_avg?

Take RLED for example:

We set the RIREF = 16.5k ohm(1.5A) and RLED[9:0] = "0100010001"b(400mA)

the waveform measurement as below.

IL_Max = 410mA (red line)

IL_Avg = 362mA (green lin)

Best regards,

Hardy

  • 0
    TI__Expert 4160 points

    Hi Hardy, 

    0x00h ~ 0x03h registers cannot modify the values of IL_max or IL_avg. Writing control bytes into current registers only set the current value in between I_min to I_ref. If you want to extend that range, please take a look at "SETTING THE NOMINAL LED CURRENT" section on page #17 of LM3435 datasheet.

    Best Regards, 

    Aaron Bing

  • 0 in reply to Aaron Bing
    TI__Expert 3640 points

    Hi Aaron,

    Sorry for unclear question.

    I would like to know which waveform value will meet register setting?

    In my previous example, we set nominal maximum current = 1.5A and RLED current value= 400mA.

    Is RLED current value will equal to measured RLED current_High (Red line in previous picture)?

    Or,

    Is RLED current value will equal to measured RLED current_Avg (Green line in previous picture)?

    Best regards,

    Hardy

  • 0 in reply to Hardy Xue
    TI__Expert 4160 points

    Hi Hardy, 

    Sorry for the misinterpretation. 

    The RLED current is equal to the measured current_Avg (green line). In case that you have any concerns with the error, please set RLED[9:0] = 11,1111,1111b = 3FFh to see if that generates a 1.5A output current. Considering the table attached below, there is a range of current accuracy that affects the 1024 steps adjustments. 

    Best Regards, 

    Aaron Bing