• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 320 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLC5916 LED driver for TFT assistance

Nick microman
Prodigy 20 points
Other Parts Discussed in Thread: TLC5916

I'm going to be doing a project using the TLC5916 LED driver which will control a TFT LCD. However, I could use some assistance as to how to properly configure and setup the driver. The display I am using requires 40mA @ 19.2V. So, I would need 40mA and 19.2V coming out of one pin (AKA one channel) to drive the LED backlight for the TFT display.

Looking through the datasheet I was able to ascertain the following:

CM=current multiplier

If CM = 1 then Iout target = (1.25V/Rext)x15
if CM= 0 then Iout target = (1.25V/Rext)x5

Also, if CM is 0 then the current output is limited to 3 to 40mA, else it is limited to 10mA to 120mA.

Using CM=0, and the equation Iout target = (1.25V/Rext)x5 and solving for Rext I get:

Iout target = 40mA
Rext = (5*1.25V/40mA) => 156.25 ohms or ~156 ohms

In addition, going off of pg. 24 of the datasheet, the 8-bit configuration code looks like:

01111111

So, my question are as follows:
1. Is the method I am using correct. Do I have the correct resistance?
2. Now that I have 40mA output current how do I get 19.2V. Do I need to take additional steps?
3. When hooked up to a microcontroller using SPI, is /OE essentially /CS?
4. How do I configure the TLC5916 to only utilize 1 channel for the output

If anyone can answer any of the above questions that would be much appreciated. Thank you.

  • 0
    TI__Genius 14890 points

    Nick,

    1. Yes, your calculations are correct.  The default value in the configuration register is 1111 1111.  It may be simpler to leave that register alone and calculate the Rext with that configuration (468.75 ohms ~ 470 ohms).  You can then use the configuration code to dim the current.  

    2.  The TLC5916 does not produce 19.2V.  It is a sink driver.  See Figure 16 in the datasheet.  "VLED" refers to the voltage supplied by the system for power to the LEDs.

    3.  OE enables the outputs.  If OE is high, the outputs are off.  If OE is low, the outputs are on.  OE does not impact communication with the TLC5916 (other than its us as ED when entering / exiting special mode).

    4. Writing to the TLC5916 in normal mode controls each output independently.  If you write 0000 0001 then only 1 output will be on.  0000 1111 turns 4 outputs on.

    Regards,

    Dick