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LM3410XBSTOVPEV: How to modify the board.

Barry Penfold
Prodigy 20 points
Part Number: LM3410XBSTOVPEV

Hello,

I am interested in your LM3410XBSTOVPEV/NOPB demo board. In its User’s Guide (AN-1996), Figure 8, it states “The evaluation board can be modified to allow the user to derive the power from an input supply that is larger than 5.5 V.” How do you modify the evaluation board to perform the Figure 8 function?

If it can be modified, I would like to run off vehicle power (13.8V). I then can add a zener diode and resistor like your LM3410 data sheet shows (Page 28, Figure 28). For the final design, I would need 1A ran through 4 LEDs from the vehicles 13.8V supply using a LM3410XQMF/NOPB.

Thank you,

-Barry

  • 0
    TI__Mastermind 28655 points

    Hello Barry,

    Page 28 and 30 of the datasheet, Figure 28 and Figure 30 shows the schematic using a separate Vpwr and Vin.  If you are planning on running 4 LEDs in series the voltage, most likely, will be less than 13.8V.  if this is the case then a SEPIC is needed.  This is an issue since the voltage on the SW node will become 13.8V + 12V (assuming 3V Vf for the leds) + V diode.  This will be approximately 26.4V.  Recommended maximum operating voltage of the SW node is 24V, abs max is 26.5V so this won't be a viable design.

    A boost requires the output voltage be higher than the input voltage.  A SEPIC can have the output big higher or lower voltage than the input.

    They way I would modify the board is to break the connection to the inductor.  Add a capacitor from the inductor to ground.  Supply the board Vin with 3.3 to 5V via a resistor and zener from the inductor connection and then supply that inductor connection with the external voltage.

    Best Regards,