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[ TLC59116 ] Natural Brightness Control

Kenichiro
Mastermind 9165 points
Other Parts Discussed in Thread: TLC59116

Hi,

My customer has been evaluating and designing the illumination lighting by using TLC59116.

They try to change the brightness of individual LEDs with IDCx[7:0], however, due to some limitations of their system, they can use only 16steps of IDCx[7:0] instead of 256steps(ie. 2^8).

Also, they expect to obtain natural brightness change for human eye (linear change) for 0% to 99.6% range.

If I simply calculate, one idea could be just using the number with each 16 values (0h, 10h, 100h....), however not sure if I can achieve natural changes.

Do you have any ideas to support this requirement?

Thanks for your support in advance.

Regards,

Ken

  • 0
    TI__Genius 14890 points

    Ken,

    The best thing to do is concentrate on the datasheet section "Output Gain Control Register (IREF)".  Figure 11 shows the current gain as a function of the value of the IREF register.  From the curve, you can see that the change is not linear.  There are several breaks along the way.  Additionally, you can see that the full range is from 1/12 (8.3%) to 127/128 (99.2%).  The only way to get 0% is to turn the output off.  For accuracy, the user must pay attention to the minimum current of 5mA.  Below 5mA,even with the IREF register, the accuracy will vary.

    Let me know if this helps.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Mastermind 9165 points

    4848.130403-TLC59116-IREF.xlsx

    Hi Dick,

    Thank you for your prompt reply!

    I have spent some times to creat IREF calculation sheet. Because of my customer requet me to show the reference value of IREF for having "natural brightness change". (I'm not sure whether customer can have "natural" brightness cange with this IREF value. They need to check and perform fine tune.)

    Can you check the spread sheet attached and my calcuration of IREF?

     

    # IREF hex Iout,target
    1 00000000 0 8.8
    2 00110000 30 15.3
    3 01001110 4E 21.3
    4 01100101 65 27.6
    5 01111100 7C 33.9
    6 10100011 A3 40.6
    7 10110010 B2 46.8
    8 10000000 80 52.5
    9 11001000 C8 59.1
    10 11010000 D0 65.6
    11 11010111 D7 71.4
    12 11011111 DF 77.9
    13 11100111 E7 84.5
    14 11101110 EE 90.2
    15 11110110 F6 96.8
    16 11111111 FF 104.2
    Note: REXT 180 ohm
  • 0 in reply to Kenichiro
    Mastermind 9165 points

    Hi Dick,

    Sorry for rushing you, but it's really appreciated if you can check my post above.

    Thanks,

    Ken

  • 0 in reply to Kenichiro
    TI__Genius 14890 points

    Ken,

    I am working on this now.  I will reply as soon as I have reviewed my information versus yours.

    Regards,

    Dick

  • 0 in reply to Kenichiro
    TI__Genius 14890 points

    Ken,

    My review shows that 80(hex) above would be transition point (causing IOUT to reduce).  I suggest C0 or C1 to replace 80.  Please verify with your calculations.

    Regards,

    Dick