l6390 STMicroelectronics, l6390 Datasheet - Page 18

• Manufacturer Part Number: l6390
• Description: High-voltage High And Low Side Driver
• Manufacturer: STMicroelectronics

Bootstrap driver
18/22
Equation 3
where Q
bootstrap DMOS and T
For example: using a power MOS with a total gate charge of 30nC the drop on the bootstrap
DMOS is about 1V, if the T
Equation 4
V
is too high, or the circuit topology doesn’t allow a sufficient charging time, an external diode
can be used.
Figure 7.
drop
V
S
has to be taken into account when the voltage drop on C
gate
D
BOOT
is the gate charge of the external power MOS, R
Bootstrap driver
a
V
HVG
LVG
drop
charge
=
charge
I
V
is the charging time of the bootstrap capacitor.
BOOT
V
ch
OUT
drop
arg
H.V.
is 5µs. In fact:
e
R
=
dson
C
30nC
-------------- - 125Ω 0.8V
TO LOAD
BOOT
5µs
→
⋅
V
V
S
drop
=
∼
------------------ R
T
Q
ch
dson
gate
BOOT
b
arg
HVG
LVG
is the on resistance of the
e
is calculated: if this drop
dson
BOOT
V
OUT
H.V.
D99IN1067
C
TO LOAD
BOOT
L6390