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Common current controle for multiple TLC5916

Alan Hackett
Prodigy 20 points
Other Parts Discussed in Thread: TLC5916

I am designing a circuit using 4 off TLC5916 to drive 4 off 7 segment LED displays.

Is it possible to join REXT inputs on all four of TLC5916 to a single resistor (variable) to control all output currents (and therefore brightness) together?

Thanks

Alan

  • 0
    TI__Expert 5275 points

    Hi Alan,

     

    I would not recommend this approach.  Especially if the drivers will have different voltage gains VG.  Each of the drivers will try to regulate the voltage on the R-EXT (as set by the voltage gain VG).  The current at the output will be a ratio compared the current sunk by the driver through the R-EXT resistor.  If all the R-EXT are tied together, there could be offset in the amount of reference current coming from each devices, causing large variation in the amount of output current.

     

    Regards,

    Adam Hoover

  • 0 in reply to Adam Hoover
    Prodigy 20 points

    Hi Adam

    I could see it would be a problem if each driver was set up differently.  In my application the drivers will be using the default set-up of the driver so they will all be the same (not taking into account any manufacturing differrences).

    I was looking for a simple way to change the brightness of the displays without using software.

    Thanks

    Alan