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CSD18534Q5A: Body diode conduction capacity

Atharva U
Intellectual 400 points
Part Number: CSD18534Q5A
Other Parts Discussed in Thread: LM5141, , CSD

Hi,

Does LM5141 along with recommended csd18534q5a, requires free wheeling diode for 10A specification

Understand that having FD is always recommended but wanted to understand from design point of view for CSD18534Q5A - current carrying capacity of body diode

Thanks

ATharva

  • 0
    TI__Mastermind 32845 points

    Hi Atharva,

    Thanks for the inquiry. A free-wheeling diode is optional. The body diode of the CSD18534Q5A can handle the same current as the FET when it is on. The only limitation is the power loss in the diode: VF x ID. The 5x6mm SON package is capable of dissipating about 3W continuous with VF = 0.6V at TJ = 125ºC, the maximum continuous forward current = 3W/0.6V = 5A. Please see the blogs in the links below for more information on how TI specs maximum and pulsed currents for our FETs.

    Best Regards,

    John Wallace

    TI FET Applications

    Continuous current ratings

    Pulse current ratings

  • 0 in reply to John Wallace1
    Intellectual 400 points

    Thanks John. Answers my question on current capacity of body diode.

    I got scared to see 5A at first, but then i realise, Body diode has to conduct only in Dead time, which is 20ns according to LM5141 datasheet. So i am thinking, I can get by without heatsink.

    With CSD's Rds on below 10mohm, with 10A, design looks safe.

    Let me know if you find my assumptions wrong.

    Will go through the links. Thanks again 

  • 0 in reply to Atharva U
    TI__Mastermind 32845 points

    Hi Atharva,

    You are welcome. TI has a number of excel-based FET selection tools including one for synchronous buck converters. You can use this to estimate the power loss in the FETs and compare up to 3 different TI FET solutions. You are correct, the body diode conduction loss will be minor compared to the on resistance conduction and switching losses of the FET.

    Thanks,

    John