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LM3409-Q1: LM3409-Q1 parameter confirmation

Alon Chen
Intellectual 370 points
Part Number: LM3409-Q1
Other Parts Discussed in Thread: LM3409

Tool/software:

Hi Team,
I have three questions about the LM3409-Q1. Could you please help me answer them? Thank you.
1. Can the LM3409-Q1's turn-on rise time and turn-off fall time be stably controlled within 2µs?
2. Can it maintain a steady-state drive current of 6.6A with a peak current of 10A?
3. Do you have any recommendations for similar chips with a steady-state current of 7A or more? Thank you.

  • 0
    TI__Mastermind 23116 points

    Hello Alon,

    This isn't a trivial question.  It depends on the operating conditions and design specifications.  This isn't a typical use case.  What is the Vin (min, max, typ)?  What load?  If LED then Vf typical and how many LEDs in series?  What is the dimming frequency and duty cycle?  Do you have a desired switching frequency?  

    1.  The LM3409-Q1 is a controller.  You should be able to get to 6.6A is you select the P-FET correctly and manage the thermals.  The LM3409 has limited drive capability so it won't do well for really large FETs or FETs in parallel.  Depending on your component selection you should be able to ramp up the current within 2 us. 

    2.  If you select components appropriately and manage thermals of FETs and diodes then probably yes. 

    3.  Most of our newer parts are monolithic so that limits the max current.  The LM3409-Q1 is a controller and give you more flexibility.  I think this is good selection and I recommend getting an EVM and then do prototyping with it to provide proof of concept.  You will need to go through design procedure and make changes to the EVM to support the higher currents, but at least you can prove it works, though thermals will not be great and you will need to address that in PCB development. 

    What is the end application for? 

    -fhoude