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LM3434SQ-20AEV: LM3434 EVM malfunctions

Ofer Merom
Prodigy 115 points

Part Number: LM3434SQ-20AEV

Hi

I tasked to design LEDs panel dimmer for up to 15A with 17V Leds strips i found the LM3434 best fit for the task and the LM3434SQ-20AEV for first evaluate.

I bought 2 units of LM3434SQ-20AEV from TI store for evaluating LEDs dimmers for LED lights panel.

I connect the evm to lab DC power supply with maximum 3A output current and to 4 x 17V ( 6 leds of 2.7V  600ma) LEDs strips and 15khz PWM   connected to between GND and PWM input.

The First board EVM the dimming not function there was no response to duty cycle change of PWM and after one minute the board stop driving the LEDs and start to consume hi current (shortcut ),Q4 and Q3 temperature rise to more then 60C.

The second EVM function  as expected. Except for when setting the PWM duty to get 100% power and the increase the PWM to reduce the output it stuck in 100% till  power down and up again.

After running the second EVM for 20 minutes it stop driving the LEDS  and the output voltage on the LEDs remain 16V and nothing help .

Please advice ?

Thanks

Ofer Merom

  • 0
    TI__Mastermind 28655 points

    Hello,

    How much power are you trying to deliver to the load?  15A * 17V = 255W

    What input voltage are you using.  3A on the power supply is not enough to deliver that much power to the LEDs.  Pin has to be greater then Pout.

    This board wasn't intended to run that much power, if you look at the graphs it shows 3V to 6V, not 17V.

    Also, the LM3434 is obsolete, I would look at other parts, the TPS92640/641 are capable of driving that much power.

    Best Regards,

  • 0 in reply to Irwin Nederbragt
    Prodigy 115 points
    Hello,
    I the evaluation board user guide wrote that the EVM design to provide a constant current in the range of 4A to 20A.
    and e input voltage of -9V to -30V.
    The power condition i have test it less then EVM ability and both EVMs stop working.
    I didn't find any reference that LM3434 is obsolete!
    The TPS92640 is newer part and look suitable for the application.
    thanks,