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I have IRS2011 high/low side MOSFET driver, for driving IFRZ44N MOSFETs configured in H-bridge. How would I calculate the bootstrap capacitor required by the IC for driving high-side?

I am aware of the equation in this pdf, but since these wont drive the H-bridge continuously I dont know what to use for the frequency. I am driving a motor with the H-bridge.

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You control the frequency so you should know exactly what it is.

The bootstrap capacitor power cannot be used if you require DC drive from the H-bridge. Each half-bridge must be driven low frequently to 'refresh' the capacitor, or the charge will leak off and the drive to the high-side n-channel MOSFET will be compromised.

If you need to drive it high continuously you must use a different type of power such as a DC-DC converter.

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  • \$\begingroup\$ Ohh, so bootstrap capacitor can be used only if the H-bdrige gets "refreshed" in a fixed amount of time? \$\endgroup\$ – Golaž Jan 9 '15 at 16:24
  • \$\begingroup\$ Yes, that's a gotcha with this kind of driver. \$\endgroup\$ – Spehro Pefhany Jan 9 '15 at 16:26

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