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CSD18540Q5B: MOSFET selection

Sumanth Nandikanti
Prodigy 20 points
Part Number: CSD18540Q5B

A brief description about my application, controlling a 40V 15A LED load, 450W with PWM from microcontroller 0-5V. The power supply has capability of 500W.

Earlier I had built a circuit to control up to 200W with the power supply, using PWM and it worked fine. When I tried controlling the 450W, the mosfet didn't give out full output. So, I had to add a gate driver and external 12V supply to completely saturate the mosfet to 10V and worked fine, but had lot of fluctuations in between. Right now, i'm reconsidering the mosfet options, and if possible gate driver options. Any help in finding me the correct MOSFET would be highly appreciated.

Under the power mosfet section, we have three options, N-channel, P-channel, Power Mosfet module.  [--Eliminating the P-channel Mosfets.]

I have come across CSD18540Q5B   as best suited for my need. 

Couple of questions for the experts: 

1. Would the Mosfet run 40V 15A if the gate voltage is 5V, or does it have to be around 10V? 

2. If the gate requires 10V, please suggest a good gate driver. 

3. Any additional knowledge about my load connections or circuit connections would be appreciated. 

 

Currently learning more about Power stage module under power mosfet, if you could suggest anything in this, as it has in built gate driver. that would be good.

Thank you

-Summi

  • 0
    TI__Mastermind 18200 points

    Summi,

    The CSD18540Q5B is a logic level device, meaning its threshold is ~1.8V. You'll note the resistance of the device is rated down to 4.5Vgs, so that is the minimum voltage we would recommend driving at. 

    So the part should be fine at 5Vgs, but if it falls much below 4.5V, we make no guarantees about performance, because at that point you are pretty high on the Rdson vs. Vgs curve (Figure 7 on the datasheet). We guarantee the max resistance at 4.5Vgs, so if you can be sure that the Vgs will be 5V, there should not be a problem.