LM3414HV: Low Current Output

Hi Yousuff,

I am currently out of office. I will reply to you on May 6th when I am back to office. Thanks for your understanding.

Best Regards,

Steven

Hi Yousuff,

May I understand which part code of the LED panel do you use?

Also, please check with the LED panel manufacturer to see if this LED module should be driven with constant-current driver or constant-voltage driver.

Best Regards,
Steven

Hi Steven, 

The part code of the LED panel that I am using is: PLDU30120.

I have also confirmed with the LED panel manufacturer that the LED module should be driven with a constant-current driver.

Kind Regards,

Yousuff.

Hi Yousuff,

• Do you build the circuit on the breadboard? If so, I do not think the IC has enough heat dissipation capability. Please check if the thermal shutdown of the IC is triggered.
• How do you connect the DIM pin?

Best Regards,

Steven

Hi Steven, 

Yes, the circuit is built on a breadboard as you can see in the image. I have soldered a copper wire onto the EP pad of the IC and added some extra copper and connected directly to PGND. Is there another way to carry this out? I was trying to prove the 1A output current concept before having a PCB made.

How do I check if the shutdown of the IC is triggered? Is there a specific way to test for this?

The DIM pin is pulled up to VCC with a 10K resistor.

Kind Regards,

Yousuff.

Hi Yousuff,

Yousuff Ansari said:

How do I check if the shutdown of the IC is triggered? Is there a specific way to test for this?

You can measure the IC temperature if possible. Or you can check if there is a repeatedly on-off-on (normal-TSD-normal...) current output, which is a phenomenon that may indicates TSD (thermal shutdown).

Best Regards,

Steven

Hi Steven,

Thank you for this.

I can confirm that I can prevent the IC from thermal shutdown if I use an external DC fan to keep the IC cool. If I point the DC fan's airflow away from the IC, the IC struggles to hold the constant current output and rapidly decreases the current output and starts to repeatedly turn ON / OFF - I'm assuming this is the triggering of the thermal shutdown? The issue is that the current output is still lower than the expected 1A.

Please see FLIR thermal imaging camera captures for more insight to how hot the chip gets:

It can be seen that the IC is operating at normal temperature which is around 36.2 degrees C.

However, adjacent to the IC, it is around 132 degrees C - I am assuming that this is where the majority of the heat is being sunk.

Any help would be appreciated! 

Kind Regards,

Yousuff.

Hi Yousuff,

What is the object that has around 132 °C temperature?

Best Regards,

Steven

Hi Steven, it is the copper tracks of the breadboard adjacent to the IC.

Please see image below of the hot area:

You can also see that the IC itself is operating at normal temperature.

Kind Regards,

Yousuff.

Hi Yousuff,

Please measure the inductor current and LX voltage. Then please show me the oscilloscope capture. Thanks.

Best Regards,

Steven

Hi Steven,

Can you please provide a schematic with points to probe? Also, what is the best way to measure inductor current? Not sure we have the equipment for it.

Kind Regards,

Yousuff.

Hi Yousuff,

For measuring LX voltage, you should probe this node close to the LX pin of the IC.

For measuring the inductor current, you should use a current probe to measure it.

Best Regards,

Steven