In this link it explains how to calculate bootstrap capacitor for IC Mosfet Driver. In the Vboot formula as shownenter image description here there is Vgsmin (minimum gate source voltage). Is Vgsmin the same as Vgs or not? Before it, i used mosfet IRF3205 and IC Driver Mosfet IR2103 and Diode FR207.

  • \$\begingroup\$ There once used to be better engineers in Onsemi :( The one who decided to name "The maximum allowable voltage drop" as Vboot is really beyond.... \$\endgroup\$
    – carloc
    Nov 4, 2020 at 7:09

1 Answer 1


You pick Vgsmin.

Vgsmin is how low you are willing to let Vgs fall before a bootstrap cap refresh. You should pick a Vgsmin no lower than that which produces the highest Rdson that you are willing to live with.

  • \$\begingroup\$ so I can freely determine the min Vgs value but shouldn't it be lower than 10V? Because the IRF 3205 datasheet Rdson 8miliohm with Vgs = 10V @DKNguyen \$\endgroup\$ Nov 4, 2020 at 3:03
  • \$\begingroup\$ Yes. I mean, you could go a bit lower but Rdson will be higher. Don't forget Rdson increases with temperature. Look at the graph later in the datasheet. \$\endgroup\$
    – DKNguyen
    Nov 4, 2020 at 3:13
  • \$\begingroup\$ thank you @DKNguyen \$\endgroup\$ Nov 4, 2020 at 4:03

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