LM3409: Customer tested the power consumption has difference between 7 boards?

Part Number: LM3409


Could you kindly help to check the below schematic, since customer tested the power consumption(The red dot in below picuture) has difference between 7 boards.

And the difference of Power consumption is about 0.4W.

The biggest power consumption is 3.4W(238.3mA/14.35V), and the smallest power consumption is 2.95W(209.4mA/14.11V).

Is it normal about the difference of 0.4W?

Btw, is there any influence about L6 in the schematic? I let customer use reference PN(TDK) to test again.

Pls. give some advice about it.

Thanks a lot!

Best regards

Luck Wu

1 Reply

  • Hello Luck Wu,

    I don't know what your input voltage is, I used 24V to calculate a few things.
    Peak current threshold using 1 ohm in parallel with 0.56 ohm is 0.693A
    Peak to peak current ripple is 0.449A
    Average LED current is 0.468A

    This is using 14V as the output, 22 uH for the inductor, 15.4 Kohm for Roff and 470 pF for Coff.

    This does not match what your numbers are above, am I missing information or is something not correct in the numbers I'm using?

    The LM3409 regulates peak current, if the peak to peak current ripple is a high percentage of average output current and the inductor value varies the average output current will vary.

    Best Regards,