HIP6020ACB Intersil Corporation, HIP6020ACB Datasheet - Page 14

• Manufacturer Part Number: HIP6020ACB
• Description: Advanced Dual PWM and Dual Linear Power Controller
• Manufacturer: Intersil Corporation

The r
the same device is used for both. This is because the gate
drive applied to the upper MOSFET is different than the
lower MOSFET. Figure 13 shows the gate drive where the
upper MOSFET’s gate-to-source voltage is approximately
V
for the bias, the gate-to-source voltage of Q1 is 7V. The lower
gate drive voltage is +12VDC. A logic-level MOSFET is a
good choice for Q1 and a logic-level MOSFET can be used for
Q2 if its absolute gate-to-source voltage rating exceeds the
maximum voltage applied to V
Rectifier CR1 is a clamp that catches the negative inductor
swing during the dead time between the turn off of the lower
MOSFET and the turn on of the upper MOSFET. The diode
must be a Schottky type to prevent the lossy parasitic
MOSFET body diode from conducting. It is acceptable to omit
the diode and let the body diode of the lower MOSFET clamp
the negative inductor swing, but efficiency could drop, in some
cases, one or two percent as a result. The diode's rated
reverse breakdown voltage must be greater than the
maximum input voltage.
P
P
CC
UPPER
LOWER
HIP6020A
FIGURE 10. UPPER GATE DRIVE - DIRECT V
-
+
less the input supply. For +5V main power and +12VDC
DS(ON)
+12V
=
=
I
----------------------------------------------------------- -
I
-------------------------------------------------------------------------------- -
O
O
is different for the two equations above even if
2
2
VCC
r
r
DS ON
DS ON
GND
V
UGATE
PHASE
LGATE
PGND
IN
V
IN
V
4-14
V
OUT
IN
CC
–
+
.
V
I
----------------------------------------------------
OUT
O
Q1
Q2
+5V OR LESS
V
IN
2
CR1
t
SW
NOTE:
V
NOTE:
V
GS
GS
CC
F
DRIVE
V
S
V
CC
CC
-5V
HIP6020A
PWM2 MOSFET and Schottky Selection
The power dissipation in PWM2 converter is similar to
PWM1 except that the power losses of the lower device are
taking place in a Schottky instead of a MOSFET. The power
losses of PWM2 converter are distributed between the upper
MOSFET and the Schottky. The following equations
describe an approximation of this distribution and assume a
linear voltage-current switching transitions.
For the fully on option (SELECT pin high) selection of the
MOSFET is based on the voltage budget available to this
regulator. Since the MOSFET is operated as a switch, its
own r
allowable across it at the maximum output current.
Where
r
DCR - output inductor DC resistance
In applications where both output settings could be engaged
(both 1.5V and fully on MOSFET) it is recommended the
MOSFET meets criteria outlined for the PWM operation as
well as the fully on operation.
Linear Controllers Transistor Selection
The HIP6020A 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.
r
P
P
DS(ON)max
P
DS ON max
MOS
SCH
LINEAR
DS(ON)
=
=
I
------------------------------------------------------------ -
I
----------------------------------------------------------- -
O
O
=
2
CE
I
- maximum allowed MOSFET rDS(ON)
=
O
V
is bound by the maximum voltage drop
r
f
V
----------------------------------------------------
is sufficiently large to provide the desired
DS ON
IN
V
V
V
V
–
IN
IN
IN
IN
DCR I
–
I
–
OUT
V
V
OUT
V
OUT
OUT
OUT
+
I
----------------------------------------------------
O
V
IN
2
t
SW
F
S