8.2.2.2 Bootstrap Capacitor

The bootstrap capacitor provides the gate charge for the high-side switch, DC bias power for HB UVLO circuit, and the reverse recovery charge of the bootstrap diode. The required bypass capacitance can be calculated with Equation 2.

Equation 2.

where

• I_HB is the quiescent current of the high-side driver.
• t_on is the maximum on-time period of the high-side transistor.

A good-quality, ceramic capacitor must be used for the bootstrap capacitor. TI recommends placement of the bootstrap capacitor as close as possible to the HB and HS pin.