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TLC59108: Does the device consumption current increase when LED is dis-connected to OUTn with OUTn on state?

Kazuya Nakai59
Guru 20785 points
Part Number: TLC59108
Other Parts Discussed in Thread: TLC59461

Hello guys,

One of my customers is considering using TLC59108 for their new products.

They used TI LED driver, TLC59461 for their past product. Then they knew the following action described on page 16 of TLC59461 datasheet is needed.

there are any unconnected output LED lamps (including connection failures or short-circuits), the grayscale data corresponding to the unconnected output should be set to '0' before turning on the LEDs. Otherwise, the VCC supply current (IVCC) increases while the constant-current outputs are on.

I heard from TI engineer long ago that this phenomenon (IVCC increasing) is caused by the base current increasing of NPN transistor for constant current output portion . 

The customer questions are followings. Could you please give me your reply for them?

Q1.  Which does TLC59108 constant current output portion (/OUT0~/OUT7) use NPN transistor or NMOSFET?

Q2.  Does the device VCC(VDD) supply current increase when LED is dis-connected to OUTn with OUTn on state?

Your reply would be much appreciated.

Best regards,

Kazuya   

  • 0
    TI__Genius 12915 points

    Hi Kazuya,

    1. The constant current output of TLC59108 is based on N-type MOSFET.

    2. The outputs are open-drain structure. When there is no pull-up path on them, they would not work and ICC would not increase. 

  • 0 in reply to Hardy Wu
    Guru 20785 points

    Hi Hardy,

    Thank you very much for your reply.

    Could I ask you an additional question?

    The customer uses TLC5915A (TI LED driver for amusement products as a slot machine) too for other products..
    Do you know this device?

    If you know the device,  does TLC5915A use same circuit as TLC59108 for constant current output portion?
    Also does the device VDD supply current not increase same as TLC59108 when LED is dis-connected to OUTn with OUTn on state?

    Thank you again and best regards?

  • 0 in reply to Kazuya Nakai59
    TI__Genius 12915 points

    Hi Kazuya,

    I did not hear about TLC5915 before. I think it is a special customized device for the customer and not public. Also the device should be old and I do not think we can find the internal circuit file.

  • 0 in reply to Hardy Wu
    Guru 20785 points

    Hi Hardy,

    Thank you very much for your reply.

    I understood that we can not find TLC5915A internal circuit no longer.

    Thank you again and best regards,

    Kazuya.