LM3409-Q1: LM3409-Q1 Minimum Output Current

Meng Liu

Intellectual 1765 points

Part Number: LM3409-Q1

Hi Expert

in the analog dim, i know Vadl can control output Led current.

but I doesn't found calculate about LED current and Vadj. i just found below information in datasheet.

could you please share the calculate method base on how many Vadj get how much Led current?

over 2 years ago

0 Shashank Kulkarni over 2 years ago

TI__Intellectual 2800 points

Please check section 8.3 of the datasheet. The behavior of the device and relation between IADJ and LED current is explained in a lot of detail.

Thanks,

Sumeet

0 Meng Liu over 2 years ago in reply to Shashank Kulkarni

TI__Intellectual 1765 points

Hi Sumeet

thanks fir your reply.

I know 8.3 have many explained but i also have one question:

if we use Iadj achieve analog dim, i can refer to below picture.

but in the 8.3.3

the relationship between IADJ and Iled as below:

if Vadj=0,the ILED is negative number？ i don't know how to explain it?

0 Tuan Tran74 over 2 years ago in reply to Meng Liu

TI__Mastermind 18550 points

Hello Meng,

Please see the below section in the data sheet where I high lighted right under the equation. What this means is as you reduce the Vadj to zero, the inductor current will go into DCM (dis-continous conduction mode) and the equation will not hold.

Thanks Tuan

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LM3409-Q1: LM3409-Q1 Minimum Output Current