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TLC59108F: I would like you to confirm that the loss calculation method is correct.

?? ??
Prodigy 40 points
Part Number: TLC59108F
Other Parts Discussed in Thread: TLC59108

・Circuit conditions    
    
LED_Vf　　　     ：1.1～1.7V
Number of LEDs ：7  
R0～R6　　　　 ：68Ω  
Icc_max　　　　：38mA ※Adjust the PWM Duty so that only 38mA flows at the maximum 
    
・TLC59108F：Calculation of allowable loss    
  　　　　　　　MAX   
OUT0_VOL　：0.4V  
P_OUT0　　 ：0.015W   ＝Vol(max):0.4V × Icc:38mA(max) 
P_OUT0-6　 ：0.1064W  ＝P_OUT0 × 7  

  • 0
    TI__Expert 4160 points

    Hi Honda-san, 

    Could you provide the schematic and elaborate on what is the exact LOSS you are trying to calculate? If you are considering the residual voltage dropped down from VLED on each channel, your calculation of power loss is correct. 

    Best Regards, 

    Aaron Bing

  • 0 in reply to Aaron Bing
    Prodigy 40 points

    Hi Mr.Aaron

    Thank you for answering.
    It will be a schematic diagram and detailed information of the configuration.

                                              

    Item Unit Value
    TYP MIN MAX
    VLED V 5 4.75 5.25
    LED_Vf V 1.4 1.1 1.7
    R0～7 Ω 68 67.32 68.68
    IF mA 20 9 38

    We have reviewed the calculation, so please check it.

    Item Unit Value
    IF A 0.009 0.020 0.038
    R0_Applied voltage V 0.606 1.346 2.558
    OUT0_Voltage V 3.544 2.804 1.592
    P_OUT0 W 0.032 0.056 0.060
    P＿OUT0-6 W 0.223 0.393 0.423
    P_Icc W 0.047
    TJ ℃ 70.578 77.194 78.404



  • 0 in reply to ?? ??
    TI__Expert 4160 points

    Hi Honda-san, 

    Sorry for the misinterpretation. I have confirmed from section 9.2.2 Detailed Design Procedure on the datasheet that your 68ohm calculation for design purposes is correct. 

    Best Regards, 

    Aaron Bing

  • 0 in reply to Aaron Bing
    Prodigy 40 points

    Hi Mr.Aaron

    Thank you for checking.

    There is something I would like to check additionally.

    I'm also considering TLC59108, which can reduce the mounting space. However, since the TLC59108F has a limiting resistor outside, is it correct to recognize that it is more advantageous as an IC loss than the TLC59108?

    Best Regards,

  • 0 in reply to ?? ??
    TI__Expert 4160 points

    Hi Honda-san, 

    I agree that TLC59108 can reduce the mounting space with less resistors. It is fair to say that TLC59108F has some power advantages, but the total power consumption in both cases are still the same. 

    Best Regards, 

    Aaron Bing

  • 0 in reply to Aaron Bing
    Prodigy 40 points

    Hi Mr.Aaron

    Thank you for your answer.

    Let me check the details.

    Is the calculation of the loss of each of the ICs of TLC59108F and TLC59108 as follows?

    ・Loss calculation for TLC59108F　　　　 ・ Loss calculation for TLC59108
    　W = (VLED－VF－VR) × IF   　 　　＜ 　　 W = (VLED－VF) ×IF 

    VF：LED forward voltage

    VR：Voltage applied to the resistor

    IF：LED current

    Best Regards, 

  • +1 in reply to ?? ??
    TI__Expert 4160 points

    Hi Honda-san, 

    I think the loss calculation in both cases are correct. 

    Best Regards, 

    Aaron Bing