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LM3410: Flash driver pulse duration

Kirti Patial4
Prodigy 30 points
Part Number: LM3410
Other Parts Discussed in Thread: PMP15027

Hello 

We are planning to use LM3410X as a flash driver in our design. For this we are following the circuit provided in datasheet in section 8.2.10 which shows 1.5A flash for 7.5V LED.

Our design needs only 1.1A for 7V LED (two 3.5V LEDs in series) getting power from a 1S battery.

What is the max duration of flash pulse that we can get?

Thanks

Kirti

  • 0
    TI__Mastermind 25500 points

    Hello Kirti,

    That really depends on your input voltage and the output capacitor value. At higher input voltages the LM3410 may be able to run at 1.1A continuously, but at lower input voltages it would current limit. But in general the current is initially supplied by the output capacitor so your approximate pulse time you can get would be governed by i=Cdv/dt where the dv is the difference between the LED Vf and what the cap is charged to using the feedback resistors.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 30 points

    Hello Clint

    Can LM3410 run continuously for 1.1A current for 3.5V output with 2.9V input in SEPIC configuration.

    Theoretically it looks possible looking at the switch current of 2.8A.

    But we are unable to simulate this as there is no simulation model is provided on the website and Webench also fails to show this configuration.

    Thanks

    Kirti

  • 0 in reply to Kirti Patial4
    TI__Mastermind 25500 points

    Hello Kirti,

    Ideally it would be able to with a 2.8A current limit. However, the current limit minimum guaranteed in the datasheet can be as low as 2.1A. The peak switch current in a SEPIC is the sum of the two inductor peak currents, so any devices that have a current limit on the low side may limit the max output current. You can check out PMP15027 for all of the equations for a SEPIC converter.

    Regards,

    Clint