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LM5176-Q1: Gate resistors and paralleling FETs

Bart Klusek
Prodigy 200 points
Part Number: LM5176-Q1
Other Parts Discussed in Thread: CSD19534Q5A, CSD18540Q5B, , LM5176, PMP21278

I made a prototype as suggested by WEBENCH, using CSD19534Q5A and CSD18540Q5B and am currently working on a larger design incorporating the power supply. I have two questions related to the project:

1. The prototype appears to handle full design power (24V, 9A) at room temperature. To make sure that it can work at higher ambient temperatures (up to 60C), I am planning to parallel the FETs. Is it safe to assume that, everything else being equal, the gate drivers will handle the additional FETs just fine?

2. Is is ever recommended and/or allowed to use small (~10 ohm) gate resistors with LM5176-Q1?

  • 0
    TI__Mastermind 31135 points

    Hi Bart,

    Thanks for considering the LM5176 in your design. 

    If you look at PMP21278 (http://www.ti.com/tool/PMP21278), you will find that the FETs have been made parallel to handle current up to 25A. With your application handling 9A, I think it will be okay to parallel the FETs and that the gate drivers will handle the FETs just fine. 

    For paralleling FETs, I think it would be best to minimize the impedance seen by the gate to the gate driver. I would suggest putting 0-ohm resistors, and then increasing the value as necessary. Increased resistance at the gate can degrade switching performance. 

    Thanks,

    Richard