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LM3409HV: Gate Driver Capability – Can It Drive 2 or 3 MOSFETs in Parallel?

Sean Hung
Prodigy 90 points
Part Number: LM3409HV

Tool/software:

Hi TI Experts,

I am using the LM3409HV to design a 6A LED driver. Due to thermal concerns, I am considering using 2 or 3 MOSFETs in parallel.

My main question is: How many MOSFETs in parallel can the LM3409HV drive? Simply put, is the LM3409HV capable of driving 2 or 3 MOSFETs in parallel?

As an example, let's consider the P-channel MOSFET BUK6D120-60P, with the following specifications:

  • Vgs,th = -2.5V
  • Qg = 18nC
  • Qgs = Qgd = 2.6nC
  • Ciss = 724pF

I appreciate your insights.

Thank you,

  • 0
    TI__Mastermind 23306 points

    Hello Sean,

    The main concern with using multiple MOSFETs is ensuring current sharing.  What FETs are you proposing is quite a small form factor and fairly high Rds_on.  I think you should be to a larger package not use multiple fets in parallel.  

  • 0 in reply to fhoude
    Prodigy 90 points

    Hi fhoude,

    Thank you for your reply. There are a few reasons why I am considering using multiple P-channel MOSFETs (BUK6D120-60P):

    1) We still have a large stock of this component.

    2) PCB layout space is very limited, so we prefer to use small-package components.

    3) Based on my calculations, the power loss on a single MOSFET is too high. To reduce power loss and distribute heat more effectively, I am considering using two or three MOSFETs in parallel.

    Therefore, I would like to know whether it is possible to drive two MOSFETs using the LM3409HV.

    However, I understand that heat dissipation is the most critical factor. If using multiple MOSFETs in parallel is not suitable, I am open to using a higher-performance MOSFET in a larger package.


    Best regards,

  • 0 in reply to Sean Hung
    TI__Mastermind 23306 points

    You should be able to drive them but because the driver is super low output impedance you might have slightly higher switching losses.  You can mitigate some of the loss in efficiency by going to lower switching frequency.  Should work.

    -fhoude

  • 0 in reply to fhoude
    Prodigy 90 points

    Hi fhoude,

    I found a P-channel MOSFET, DMP6018LPSQ-13.

    The detailed parameters are listed below:
    1) Vds= -60V,

    2) Ids= -48A,

    3) Vgs(th),max= -2.5V

    4) Rds,on,max= 18mR

    5) Ciss= 3505pF

    6) Qg= 13.7nC

    7) tr= 6.7ns

    8) tf= 7.2ns

    9) RJC= 1.1 C/W

    could you please have a look is it possible to use this P-MOSFET single or use it x2 connected in parallel?

    Thank you.

    Sean