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MOSFET gate resistance and dead time for ISL81601

DB

Hello! 

ISL81601 datasheet states: 

"The ISL81601 incorporates an adaptive dead time algorithm that optimizes operation with varying MOSFET conditions. This algorithm provides approximately 16ns dead time between the switching of the upper and lower MOSFETs. This dead time is adaptive and allows operation with different MOSFETs without having to externally adjust the dead time using a resistor or capacitor. During turn-off of the lower MOSFET, the LGATE voltage is monitored until it reaches a threshold of 1V, at which time the UGATE is released to rise. Adaptive dead time circuitry monitors the upper MOSFET gate voltage during UGATE turn-off. When the upper MOSFET gate-to-source voltage drops below a threshold of 1V, the LGATE is allowed to rise. Renesas recommends not using a resistor between the driver outputs and the respective MOSFET gates, because it can interfere with the dead time circuitry." 

https://www.renesas.com/us/en/document/dst/isl81601-datasheet?r=501771

page 41

So it sugest not to use resistors at MOSFET gates. 

However shematics of DEMO1Z and DEMO2Z boards include 2R2 resistors for MOSFET gates. 

https://www.renesas.com/us/en/document/mat/isl81601demo1z-user-guide?r=1500826 

page 10 

https://www.renesas.com/us/en/document/mah/isl81601demo2z-users-manual 

page 16

What is the explanation of this contradiction?

Best regards Dominik Bejma




[locked by: AK_Renesas at 10:05 (GMT 0) on 3 Oct 2024]
  • 0

    Hi, 

    Let me check and come back to you

    Thanks 

    AB

  • +1

    Hi Dominik,

    I understand there’s some confusion between the datasheet and the evaluation board schematic regarding the use of gate resistors. Let me clarify:

    The gate resistor in schematic is used to mitigate EMI and EMC effects. These effects can vary based on factors such as the type of MOSFETs used, board parasitic, operating frequency, and circuit topology. Without a gate resistor, you might encounter high current consumption, glitches at startup, or even potential MOSFET failures.

    For reliable operation, especially during the design phase, it’s advisable to use a 2.2Ω gate resistor (which should not interfere with your dead time). This will help manage practical issues and stabilize the system. Once your system is stable and if you find that the rise time of your MOSFETs is adequate, you might consider experimenting with removing the resistor.

    Kindly, update me if you need more mathematical calculations.

    Regards,

    Avinash Kumar