ISL6524A Intersil Corporation, ISL6524A Datasheet - Page 14

• Manufacturer Part Number: ISL6524A
• Description: VRM8.5 PWM and Triple Linear Power System Controller
• Manufacturer: Intersil Corporation

ISL6524A
FIGURE 13. UPPER GATE DRIVE - DIRECT V
-
+
+12V
VCC
GND
UGATE
PHASE
LGATE
PGND
14
Q1
Q2
+5V OR LESS
CR1
NOTE:
V
NOTE:
V
GS
GS
CC
≈
≈
DRIVE
V
V
CC
CC
-5V
Linear Controllers Transistor Selection
The ISL6524A linear controllers are compatible with both
NPN bipolar as well as N-channel MOSFET transistors. The
main criteria for selection of pass transistors for the linear
regulators is package selection for efficient removal of heat.
The power dissipated in a linear regulator is
Select a package and heatsink that maintains the junction
temperature below the maximum desired temperature with
the maximum expected ambient temperature.
When selecting bipolar NPN transistors for use with the
linear controllers, insure the current gain at the given
operating V
output load current when the base is fed with the minimum
driver output current.
In order to ensure the strict timing/level requirement of
OUT4, an NPN transistor is recommended for use as a pass
element on this output (Q5). An low gate threshold NMOS
could be used, but meeting the requirements would then
depend on the VCC bias being sufficiently high to allow
control of the MOSFET.
P
LINEAR
=
CE
I
O
×
is sufficiently large to provide the desired
(
V
IN
–
V
OUT
)