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TLC59116 Vol

Jamaal_Charles
Genius 3245 points
Other Parts Discussed in Thread: TLC59116, TLC59116F

Hello,

We are looking at using the TLC59116 in our design, but can't figure out what VOL stands for.  Our assumption is that it is the dropout of the device, but what is the value of VOL?  It is referenced in the datasheet as follows.

Figure 2 shows the output voltage versus the output current with several different resistor values on REXT. This

shows the minimum voltage required at the device to have full VF across the LED. The VLED voltage must be

higher than the VF plus the VOL of the driver. If the VLED is too high, more power will be dissipated in the driver.

If this is the case, a resistor can be inserted in series with the LED to dissipate the excess power and reduce the

thermal conditions on the driver.

Any clarification would be helpful.

Thank you

  • 0
    TI__Expert 3460 points
    Hi Jamaal,

    VOL is the minimum voltage needed in order to sink the expected current on the output pin. Each line in figure 2 shows that when you sweep the output voltage, the output current will increase to a certain value. For your design, you want to look at the expected output current, and make sure the voltage seen at the output pin is high enough for the device to sink the expected current (the flat region of figure 2). Based off the graph data, I would use 1V as a rule of thumb.
  • 0 in reply to Harry Kennedy1
    Genius 3245 points
    So,

    That is a problem. Even a 0.5V wouldn't work.

    Is there a way to “disable” current limiting in the chip, and just let an external resistor take care of it? We are going to have to combine some LEDs in parallel, while others get their own driver output, I thought it would be better to open the driver wide open (not let it control current for me), and just let the external resistors control current. It would then be the equivalent of the LED driver acting as a transistor of sorts.

    If there’s a way to “disable” the current control of the IC, I’m hoping that would alleviate the need to have a specific voltage on the output pin (for it to regulate).

    Thanks,
    JC
  • 0 in reply to Jamaal_Charles
    TI__Expert 3460 points
    Sorry for the delay Jamaal,

    The TLC59116F device will do just that. On each output, the designer would place a current limiting resistor.

    Can you talk more about the application? what is the output voltage used to drive the LEDs? what is the current of the LEDs? Can you draw a picture of the planned LED structure? If I have more information, I can help you come up with the best overall solution.
  • 0 in reply to Jamaal_Charles
    TI__Guru 71526 points
    E,
    Can you follow-up with this, please?
    ~Leonard