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TLC59116 Overheat Problem

Andy Warne
Intellectual 615 points
Other Parts Discussed in Thread: TLC59116

Hi,

 

We have in production a USB LED controller using 4 x TLC59116.

Each IC drives 16 LEDs at 20mA. REXT is 715 Ohms. IREF is E0h

VLED is 5 volts when we use conventional LEDs but we also have installations with 5 volt LED lamps with a series resistor and for these VLED needs to be 12 volts to get sufficient current.

The TLC59116 ICs were noted to be running extremely hot at over 80 degrees. After approx 30 seconds of operation with all LEDs lit, the LEDs suddenly go into a dim mode where all of them reduce in brightness slightly. We fitted heatsinks to the TLC ICs and this eliminated this problem.

Thinking we were good to go, we went into production and now we are getting a large number of falures after a couple of days operation, with single channels initially flickering then staying permanently lit, even during and after a hard or soft reset.

Something must be wong here but what?

Note I raised a support request some time ago before posting here but this has not been followed up other than by a sales person. 

 

  • 0
    Prodigy 30 points

    I have encountered a similar(same) issue with this part.  Rext set at 360 ohms, using default register settings for all current gain.

    Vcc is 5V, VLED is 12.  After a long period of continuous use (usually > 100 hours) we see channels failing conductive to ground (LED staying on).

    Did you ever make any progress on this issue?

  • 0
    Prodigy 90 points
    Sorry for the thread necro, but I do have an answer, for what it's worth.

    The part will have to dissipate power based on the usual Ohm's Law stuff, so current times whatever voltage it has to drop. Raise the voltage and the power dissipation goes up as well. Jump from 5v to 12v with no other changes and the chip now has to dissipate another 2.24 watts! (Given your specs.)

    Use a larger value series resistor (and be careful of your power dissipation there as well!), supplement with series diodes (same comment), or use a power supply with a lower voltage. For the latter I tend to design in a circuit with a variable switching regulator when I can.

    Contrariwise, if the LEDs are all the same brightness or can be controlled in groups, you should be able to wire two or three in series and use your 12v supply with much less hassle.

    Obviously the answer depends on your actual requirements.