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UCC27511: Low Side Gate Driver for Drive TWO PARALLEL MOSFET

Michele Bonollo
Prodigy 200 points
Part Number: UCC27511

Hi, I want use TI Mosfet Gate Driver UCC27511 for drive TWO PARALLEL MOSFET. 


I have a doubt:
1) The connection of the two output (OUT_SRC / OUT_SNK) with resistor at the two Mosfets ???  may be correct the sink and source resistor and the circuit topology ?

I need a non inverting applications with classic high level PWM->Motor ON, low level PWM->Motor OFF  to Pin IN+

attach the electrical drawing of the part of my project.

Thank you

  • 0
    TI__Expert 3355 points
    Hi Michele,

    I'm an applications engineer with the high power drivers group and can help you with your question. Thank you for attaching the schematic, that helps a ton.

    Your schematic looks correct for the driving these transistors, though I can recommend a few improvements and cautions. The 1nF caps (C4 and C5) can be good to test the drive strength, but make sure they are not populated in the final schematic. Put 10k pull down resistors on the MOSFET gates. Also it would be good practice to put clamping diodes on the gates.

    The FET you selected looks to be capable of driving your motor with just one FET, operating up to 80A continuous compared to your 20A spec. You could feasibly drop this down to a 1 FET design if needed.

    It would be good to add an input filter and pull down resistor on the actively PWMed IN+. Is L1 a ferrite bead? This extra inductance will be in your drive current path and will affect how fast you can turn on and off the FETs. If running a split ground, you should keep the driver bypass caps referenced to GND_Motor, and the IN+ filter referenced to GND_P.

    If this helped answer your question, can you please press the green button?

    If not, feel free to ask follow up questions and we'll get back to you as soon as possible.

    Thanks and best regards,
    John
  • 0 in reply to John Geiger
    Prodigy 200 points
    Hi and thank you very much for your assistance, summing up i correct with your suggestions:

    -Yes the C4, C5 capacitor are Not mounting; i use it only for EMI Tests, instead of these two capacitor I can put a zener diode (BZX85B13) Only if i have Gate overshoot problem with the PCB layout.
    -Yes i have added a resistor near to Gate/Source pin of every Mosfet, I was in doubt for the value between 10K and 22K (I see your reference design) for this high Power Mosfet's i think put 12K
    -Yes for security i choose very large Mosfet High VdssMax, IdssMax and very low on Rdson (10,7mOhm)
    the reason is because I have a small and poorly sized heat-sink. During the test, if I get satisfactory results, I will mount only one Mosfet
    -Ok i added a C filter and pull-down capacitor on the Net PWM_M that come from my microcontroller STM STM32F100 RBT6B
    -Yes i change the ground topology, i use very often the ferrite bead in the ground isolation for EMI-suppression immunity. But in this case for not to penalize the switch on/off rising/falling edge, i have change and connected the GND_MOTOR to IC4 IN-, GND pin and to the C1, C2, C3 bypass capacitor, while the PWM_H microcontroller pin is referred to the GND_P (that is the same GND but with EMI ferrite filter)

    May be all OK ??
    Thank you
  • 0 in reply to Michele Bonollo
    TI__Genius 13445 points
    Hi Michele,

    The ferrite bead is a nice bonus, which I've generally seen on the gate of the MOSFETs to suppress as you mentioned high frequency EMI noise and prevent false turn-on/off of the FET, but again it is a bonus and not necessarily a requirement.
    Overall the changes you made seem reasonable.

    Please let us know if you run into issues or need further assistance.

    Regards,

    -Mamadou
  • 0 in reply to Mamadou Diallo
    Prodigy 200 points
    Thank you very much, perfect! I proceed with the design
    Talk to you soon
    Best regards

    Michele