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Some TLC59116 questions

Bart Schapendonk
Prodigy 20 points
Other Parts Discussed in Thread: TLC59116, TLC59116F

disclaimer: I'm a hobbyist, not a electronics engineer

I'm planning on using three TLC59116 (TLC59116IPWR / TSSOP) to drive six 7 segments displays (Kingbright SA23-12SRWA) for a clock project

The segments have a forward voltage of 7.4V typical (max 10V) and 3.7V (max 5V) for the decimal point, the current is 20mA

ps. I2C / SPI is a hard requirement since I will be using a Raspberry Pi 2 running Windows 10 IoT Core

Questions

  1. Can i use a VLED of 9V, or is this to low and should I use a VLED of 12V
    1. I'm planning of using a standard plug pack of either 9 or 12V
    I'm afraid of having power dissipation issues with a VLED of 12V
    1. eg. 12V - 7.4V * 20mA * 14 channels + 12V - 3.7V * 20mA * 2 channels = 1.62W i'm guessing this is on the high side already
  • Is 931ohm the correct value for a 20mA current?
  • For addressing, can i just connect an "A" pin to VDD or should I use a pull-up
  • Considering 1 and 2, might I be better of user the TLC59116F with external resistors for the segments

Regards,

Bart

  • 0
    TI__Expert 3460 points

    Hi Bart,

    Thanks for sending such detailed questions. Here are my responses

    1. Since the max forward voltage is 10V, you will need to use the 12V rail for VLED so that you have enough voltage drop for extreme cases.
    2. The power dissipation would be a concern. Are you able to use the RHB packaged device? This has a thermal pad which will help dissipate the heat.
      1. You can also configure the device to PWM to lower the average power. The Group PWM will allow you to have all of the segments PWM at the same duty cycle.
    3. For the resistance value, 931 ohms was the correct value to use.
    4. For addressing, you can tie the A# pins directly to VDD
    5. Considering 1 and 2, it might be a better idea to find a 7 segment display with a tighter Forward voltage characteristic. For example, the LTS-4301JR has a 2.0V typical, and a 2.6V max forward voltage. I would check what other 7 seg displays are out there with a forward voltage closer to the VDD value you end up using.
    1. The other thing to worry about is how you're going to configure the decimal point since it has a lower Vf on the current 7 segment display you have.

    Please let me know if you have any more questions, and have fun building!

  • 0 in reply to Harry Kennedy1
    Prodigy 20 points

    Thanks for the answer.

    I'm planning on making a one-off PCB and hand-solder it myself, so the RHB package is not an option.

    So I'm going to play it safe and use the TLC59116F and give myself some extra smd (0805) solder practice with the current limiting resistors for the leds

    Pd = I^2 * Ron

    Ron is 1.5ohm typical (TLC59116F chapter 6.5 and 9.2.1), but say its 5 ohm (worst case)

    20mA ^ 2 * 5 ohm * 16 channels = 32mW aka way below the max 1.6W at 25C ambient

    Most of the power will be dissipated in the current limiting resistors instead of the TLC59116F

    Regards,

    Bart