Bootstrap driver

L6494

14/18

DocID030317 Rev 2

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

bootstrap DMOS 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 8. Bootstrap driver with external high voltage fast recovery diode

Vdrop

30nC

5

s

--------------- 175

 1V





=

TO LOAD

H.V.

HVG

LVG

CBOOT

DBOOT

BOOT

VCC

OUT