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I am trying to design a BMS circuit by using BQ77915 . My charge and discharge mosfets are CSD18534KCS. They are only using for switching. The problem is BQ77915 datasheet says for gate resistors of CHG/DSG FETs that "System designers should adjust this parameter to meet the desirable FET rise/fall time." CHG and DSG pins output voltage is typical 12 Volts, its maximum output current is 1 mA.

So, if I want the rise time as 1 milisecond in CHG and DSG FETs; how should I choose the gate resistor value?

In my opinion; the charge that I have to give is, Q=CV where Ciss is 1500pF on mosfet datasheet and V=12 V from BQ77915. So, Q=18 nC. And, Q=Igate times ton(1ms) then, Igate is 18 mikroAmper. Rgate=83K ohm from V/Igate. Do you think I am right? Or what is the idea of this adjusting?

Thank you in advance

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  • \$\begingroup\$ What current are the MOSFETs controlling. Bigger current for the same rise time requires a lower value of resistor. You might serve yourself better if you simulated your charge/discharge circuit. \$\endgroup\$
    – Andy aka
    Commented Jan 10, 2023 at 13:38
  • \$\begingroup\$ Mosfets are controlling up to 8A. Thank you, I will try to simulate. @Andy aka \$\endgroup\$
    – Nafi Can Ereli
    Commented Jan 10, 2023 at 16:25

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