LM3409: Line Regulation

Beha Steffen

Prodigy 40 points

Part Number: LM3409

Dear all

We use the LM3409 for a LED modul

Vin 22V-26V

Iout 1A (0,2A – 1A Analog Dimming)

Now we have problems with the line regulation. Over the input voltage the output current vary form 0,9A to 1,1A.

We think that the output current should be constant over the input voltage.

Regards

over 6 years ago

0 Tuan Tran74 over 6 years ago

TI__Mastermind 18890 points

Hi Beha,

Can you forward me your schematic and load requirements on this before I can answer your question.

Thanks Tuan

0 Beha Steffen over 6 years ago in reply to Tuan Tran74

Prodigy 40 points

0 Beha Steffen over 6 years ago in reply to Beha Steffen

Prodigy 40 points

0 Tuan Tran74 over 6 years ago in reply to Beha Steffen

TI__Mastermind 18890 points

Hi Beha,

What is the part number and current rating for L200? Can I have a scope capture of the current on the inductor. You can do this by lifting up the inductor and have a wire loop with a current probe on it.

Thanks Tuan

0 Beha Steffen over 6 years ago in reply to Tuan Tran74

Prodigy 40 points

Hi Tuan

Thanks for your answer!

The part number for L200 is WÜRTH ELEKTRONIK WE-LQS 74404084220

IR 2,10A

Isat 2,60A

0 Tuan Tran74 over 6 years ago in reply to Beha Steffen

TI__Mastermind 18890 points

Hi Beha,

My simulation shows that you should get less than 2% variation on output current wit VIN varying from 22V to 26V. That's a lot less than your 10% (0.9A -1.1A) variation and there is something with your circuit. Please verify that voltage on IADJ does not vary as you change input voltage.

Another thing is the inductor current above show 1.79A average and not the 1A output.

Thanks Tuan

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LM3409: Line Regulation