LM3409HV: Driver design

Simone Valmacco

Part Number: LM3409HV

Hi,

I'm designing an led driver to power a 0.75A 41.5V led board.

I've tryed to use the datasheet and the examples provided but I'm not sure about some components, expecially L1 and R sense.

On my protoboard I've used 18uH and 0.27Ohm as current sense. I am unsure about ΔiLED-PP and ΔiL-PP value.

I want to be as close as possible to the 0.75A current output, (or a little below that)

Hope you can help me.

Best regards

Simone

over 1 year ago

0 Xiaoguang over 1 year ago

TI__Genius 17640 points

Hi, Simone,

You may refer to datasheet 9.2 Typical Applications and calculate them step by step. For example, 9.2.1 wo output capacitor and 9.2.2 with output capacitor.

Regards,

0 Simone Valmacco over 1 year ago in reply to Xiaoguang

Prodigy 30 points

Thank you very much for your reply! Can you please help me with ΔiLED-PP and ΔiL-PP values? In the examples these are provided but I don't know how to calculate them..

Thank you!

Simone

0 Xiaoguang over 1 year ago in reply to Simone Valmacco

TI__Genius 17640 points

You may roughly calculate ΔiL-PP with equ. 8

For ΔiLED-PP , if you don't have output capacitor, then it is same with ΔiL-PP.

If there is output capacitor to reduce ΔiL-PP ripple, then use equ. 19 and equ20. Refer to 9.1.5 for r_Dcalculation.

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LM3409HV: Driver design