Bootstrap driver

L6399

12/18

DocID030402 Rev 2

For example: using a power MOS with a total gate charge of 30 nC the drop on the

bootstrap diode is about 1 V, if the Tcharge is 5 s. In fact:

Equation 4

Vdrop has to be taken into account when the voltage drop on CBOOT is calculated: if this drop

is too high, or the circuit topology doesn’t allow a sufficient charging time, an external diode

can be used.

Figure 6. Bootstrap driver with high voltage fast recovery diode

Figure 7. Bootstrap driver with internal charge pump

Vdrop

30nC

5

s

--------------- 120

 0.72V





=