0
\$\begingroup\$

I want to make a circuit that has to drive more than 20 LEDs that need to be bright on a single PCB. Each LED will have to be turned on independently based on information received. Power is going to be delivered via a 12V car battery and has to be brought down to MCU voltages 3V3 or 5V.

My idea is to have an MCU and LED driver IC - TLC5951DAP for example which is going to give me the needed pins to drive all of the LEDs. The problem is that if say I want to drive these LEDs at 10mA (as I said I want them to be bright), there is going to be a lot of power dissipated by the LDO. By the calculations I did, the LDO will have to dissipate 3.52W which is well above the 0.54W it is rated to handle. Is there any way to get around this?

Another idea I had is to make transistor LED pairs which will have to be turned on by a different IC which I have not yet figured out.

I am also open to other suggestions.

\$\endgroup\$
2
  • \$\begingroup\$ Use a buck converter instead of an LDO? \$\endgroup\$ – user253751 Nov 9 '16 at 22:05
  • \$\begingroup\$ Have you tried using a voltage regulator to step down the voltage then connecting the LED and a suitable resistor in series (at least 1/4W 100 ohm) from a mcu output pin to the lower voltage? \$\endgroup\$ – user116345 Nov 9 '16 at 23:04
1
\$\begingroup\$

Power is going to be delivered via a 12V car battery and has to be brought down to MCU voltages 3V3 or 5V.

... TLC5951DAP ...

From the datasheet:

  • LED Power-Supply Voltage up to 15 V

There is no need to have the LEDs connected to the regulator. Have them connected directly to the 12V supply and let the driver handle it. As long as you use the HTSSOP-38 package with the PowerPAD soldered you should be able to withstand at least 2.5W which is within the (12V − 2V) ⋅ 10mA ⋅ 20 = 2W maximum power handling required.

\$\endgroup\$
2
  • \$\begingroup\$ The LED Driver can withstand that power but doesn't that power need to be delivered from the LDO regardless from the fact that the LEDs are connected to the car battery? As far as I understand the LED Driver outputs a fixed current and acts as a current sink at the same time. \$\endgroup\$ – Ignat Georgiev Nov 11 '16 at 12:59
  • \$\begingroup\$ The driver does not and cannot source any current. See figure 4 in the datasheet. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 11 '16 at 13:04
1
\$\begingroup\$

There are thousands of ways to solve your problem less primitively, more efficiently and at low cost.

enter image description here

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.