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LM3433SQ-14AEV: LED Driver check, current output measurement and LED dimming

Jonah Romeo
Prodigy 30 points

Part Number: LM3433SQ-14AEV

Hello,

I recently purchased an LED Driver to make a projector brighter. 

However, before I do any work, I want to test the main features of the LM3433. I am using a power supply to apply -12V, and connected a Luminous LED (SST-90) to the LED+ and LED- test post on the LM3433 to since its supposed to work with a current of 1 to 9A, and the LED driver is said to supply 4 to 20A.

My problem is that the LED is not ON. Am I missing something really basic?

  • 0
    TI__Mastermind 25500 points

    Hello,

    Please check to make sure the shunt between ADJ and POT on J2 is in place or ADJ is driven directly or it will be at CGND. It's always also a good idea to check the potentiometer as they have been known to be problematic on rare occasions. Also make sure to check the EN pin to make sure it is high.

    Let me know if you still have issues after checking those.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 30 points

    Hello Clint,

    Thank you so much for your quick response!

    I am attaching a picture of my set up because I am unable to find the error, I believe is very unlikely that the board is defective, and pretty sure I am doing something really wrong but can't point it. Can you please invest one or two minutes?, I am certain that someone with your experience can help me.

    So far I haven't weld anything, and cables are secured with reusable adhesive. 

    I am trying to turn the LED ON and measure its current, I am applying -12V with a +12 power supply, and +5V to the PWM pin using an Arduino Uno. The LED is -tied- to the LED- & LED+ pins.

    Thank you again!

    JR

  • 0 in reply to Jonah Romeo
    TI__Mastermind 25500 points

    Hello Jonah

    If you are applying 5V to the PWM pin you are turning on the shunt FETs so that is where the current will flow. You need to pull PWM low to enable the LED.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 30 points
    Hi Clint,

    To put the PWM low, does that means that I have to set 0V??, if I have a digital input to the PWM, this would either be 0v or 5v, which is what I am doing right now with the Arduino.

    Shouldn't the LED turn on if I remove the Arduino and only leave the 12V power supply?

    Best,
    JR
  • 0 in reply to Jonah Romeo
    TI__Mastermind 25500 points

    It should if you don't apply voltage to the PWM test point. You can ground it to be sure that something doesn't couple in since there is no pulldown. But also check that the POT is measuring correctly.

    Regards,

    Clint