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LM3410: 525Khz LED Driver with 100uH inductor has efficiency less than 50%

Part Number: LM3410

Hi,

I am testing on evaluation board LM3410XBSTOVPEV. I have replaced on board X type driver with LM3410Y type which has 525KHz switching frequency. And 3.3uH has been replaced with 100uH inductor.

I have set the feedback resistor value for 100mA current

Based on calculations the avg inductor should be 421mA, but when measured it is coming out to be 800mA, also the inductor is making humming noise.

Inductor part number SRR1206-101YL URL: https://www.digikey.in/product-detail/en/bourns-inc/SRR1206-101YL/SRR1206-101YLTR-ND/2352877

The reason for using the high value inductor is I have low load current at 20mA and high load current at 100mA.

Does 525KHz LM3410  not stable at 100uH inductor value? What should be the maximum value of inductor to get minimum ripple at 100mA? 

  • Hello Vidya,

    Can you let me know what the input and LED stack voltages are? Is the rest of the EVM original other than the inductor and the IC? If you changed the IC can you confirm that the DAP is properly soldered down? If it isn't that can cause issues as can a cold solder joint on a pin (I know these packages can be difficult to solder by hand).

    You may want to try and make sure the IC/DAP is properly soldered down first. If you still have issues let me know about the other things and I'll look into it further. But it should be ok with that inductor although this device and run in discontinuous conduction mode so such a high value isn't really necessary, but it's fine if you want really low inductor ripple current.

    Regards,

    Clint