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TLC5971: String led lighting driver design

Lidong Yu
Intellectual 1756 points
Part Number: TLC5971
Other Parts Discussed in Thread: , TLC5973, TLC59731

Hi, we need your technical support for our new electronic design with the TI TLC5971/TLC59711.

Please could you confirm us capability of this chip for theses specific pins interconnections in purpose to supply 3 more time current 
throw 180mA string led :

 Without interconnection : 60mA per channel

With 3 interconnections (for example OUTR0, OUTG0 and OUTB0) : 3x60 =180mA per string led

In this last case, percentage led current stability will be the same than for a 60mA per string led ?

  • 0
    TI__Mastermind 19015 points

    Hi Lidong,

    As is mentioned in the datasheet of TLC5971 / TLC59711, Multiple outputs can be configured in parallel to increase the constant-current capability.

    Lidong Yu said:
    With 3 interconnections (for example OUTR0, OUTG0 and OUTB0) : 3x60 =180mA per string led

    You are correct. Three interconnections can give you 180 mA output current capability per LED string.

    Lidong Yu said:
    In this last case, percentage led current stability will be the same than for a 60mA per string led ?

    Paralleling outputs may reduce the stability of the LED driver if the PCB layout is poor. When paralleling multiple outputs, special attention should be paid to avoid the possible oscillation caused by long trace of the output and its parasitic inductance. 

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    TI__Intellectual 1756 points

    we need to confirm with you results between 2 differents configurations for increase string led current
    (180mA instead of 60mA) :

    1- OUTR0, OUTG0 and OUTB0 are connected together
    2- OUTR0, OUTR1 and OUTR2 are connected together

    1 vs 2 : Is it the same result for current stability inside the leds strings ?

    We need to identify another TI led driver chip for 150mA output current by channel, 4-Channels or more with
    a single-wire interface (EasySet) like theses TLC5971 or TLC5973 components.

    Could you help us to identify the best solution ?

  • 0 in reply to Lidong Yu
    TI__Mastermind 19015 points

    Hi Lidong,

    • Recommend connecting adjacent pins (connection 1 as you mentioned) to reduce trace length and therefore improve stability when paralleling multiple outputs.
    • We only have TLC5973 / TLC59731 that implements a single-wire interface.

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    TI__Intellectual 1756 points

    thanks a lot. About functional block diagram on page 14 of TLC5971 datasheet, we need to precise electronic design of theses specifics blocks : 12-Channel Constant Sink Current Drive and Reference Current Control.
    How it works and which clock frequency is used for constant sink current, ripple and noise, flickering free... ?

    Please have a look to our electronic design attach file and give us you feedback about it, advices and so on... Regards, Patrice

    Electronic_Design.pdf

  • 0 in reply to Lidong Yu
    TI__Mastermind 19015 points

    Hi Lidong,

    The LED supply voltage should be no larger than 17V.

    BR,

    Steven

  • 0 in reply to Steven Li
    TI__Intellectual 1756 points

    what kind of problem will be generated by led power supply upper than 17V ? Our led power supply (48VDC) is not use for VCC and Vref pin on TLC5971. We use separate power supply.

    17V is maximum voltage level for TLC5971 internal regulator ? Led power supply too ? 

  • +1 in reply to Lidong Yu
    TI__Mastermind 19015 points

    Hi Lidong,

    17V is the maximum voltage level for both TLC5971 internal linear regulator power-supply and LED power-supply, as is mentioned in the first page of the datasheet (a screenshot is shown below).

     

    You can also refer to Section "6.3 Recommended Operating Conditions" from the datasheet. See below screenshot and yellow marks:

    BR,

    Steven