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LT3478 P-Channel FET

Hi,

I'm working on a design for a boost-buck LED driver based around the LT3478.

Examples of boost, buck and boost-buck typologies are included in the datasheet in schematic form, and in some cases, a P-Channel FET is included.

However, there doesn't appear to be any explanation for when this part is required and I'd appreciate some further guidance.

Thank you,

Jeremy.

  • Hi Jeremy 

    Are you pertaining P-MOS on Page 21 and 22? 

    If yes, they are used to cut the supply of the LED. This method implements PWM dimming scheme to control the brightness of the LED

    Regards

  • Hi Support,

    I have ordered an evaluation module and would like to implement the circuit shown as Figure 4 in the QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 949A-A/949A-B 4.5A BOOST LED DRIVER WITH PWM DIMMING.pdf

    Can you provide some further information on how to go about doing this?  Page 8 suggests that I will need to fit Q2, R21 and R20.  Can you please advise if the parts on page 21 of the datasheet are suitable and if there are footprints on the board ready for them?

    Finally, are any other parts required?

    Thank you,

    Jeremy.

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