HIP6005 INTERSIL [Intersil Corporation], HIP6005 Datasheet - Page 10

• Manufacturer Part Number: HIP6005
• Description: Buck Pulse-Width Modulator (PWM) Controller and Output Voltage Monitor
• Manufacturer: INTERSIL [Intersil Corporation]

temperature by calculating the temperature rise according
to package thermal-resistance specifications. A separate
heatsink may be necessary depending upon MOSFET
power, package type, ambient temperature and air flow.
Standard-gate MOSFETs are normally recommended for
use with the HIP6005. However, logic-level gate MOSFETs
can be used under special circumstances. The input voltage,
upper gate drive level, and the MOSFETs absolute
gate-to-source voltage rating determine whether logic-level
MOSFETs are appropriate.
Figure 10 shows the upper gate drive (BOOT pin) supplied
by a bootstrap circuit from V
develops a floating supply voltage referenced to the PHASE
pin. This supply is refreshed each cycle to a voltage of V
less the boot diode drop (V
conducts. Logic-level MOSFETs can only be used if the
MOSFETs absolute gate-to-source voltage rating exceeds
the maximum voltage applied to V
NOTE: V
Where: D is the duty cycle = V
FIGURE 10. UPPER GATE DRIVE - BOOTSTRAP OPTION
G-S
P
P
t
F
SW
HIP6005
COND
SW
S
+
-
is the switching frequency.
+12V
VCC
is the switching interval, and
= 1/2 I
V
CC
= I
O
- V
O
2
D
.
V
r
DS(ON)
+ V
IN
GND
D
BOOT
BOOT
UGATE
PHASE
D
D
t
-
CC
SW
) when the schottky diode, D2,
10
. The boot capacitor, C
OUT
D
F
CC
C
S
BOOT
/ V
.
IN
,
(NOTE)
+5V OR +12
Q1
D2
BOOT
CC
HIP6005
,
Figure 11 shows the upper gate drive supplied by a direct
connection to V
converter systems where the main input voltage is +5V
or less. The peak upper gate-to-source voltage is
approximately V
power and +12VDC for the bias, the gate-to-source voltage
of Q1 is 7V. A logic-level MOSFET is a good choice for Q1
under these conditions.
Schottky Selection
Rectifier D2 conducts when the upper MOSFET Q1 is off. The
diode should be a Schottky type for low power losses. The
power dissipation in the schottky rectifier is approximated by:
In addition to power dissipation, package selection and
heatsink requirements are the main design trade-offs in
choosing the schottky rectifier. Since the three factors are
interrelated, the selection process is an iterative procedure.
The maximum junction temperature of the rectifier must
remain below the manufacturer’s specified value, typically
125
and the schottky power dissipation equation (shown above),
the junction temperature of the rectifier can be estimated. Be
sure to use the available airflow and ambient temperature to
determine the junction temperature rise.
Where: D is the duty cycle = V
P
IGURE 11. UPPER GATE DRIVE - DIRECT V
COND
HIP6005
o
+
-
C. By using the package thermal resistance specification
+12V
V
= I
f
is the Schottky forward voltage drop
0
V
x V
CC
CC
f
CC
x (1 - D)
GND
. This option should only be used in
BOOT
UGATE
PHASE
less the input supply. For +5V main
OUT
Q1
+5V OR LESS
/ V
D2
IN
, and
NOTE:
V
CC
G-S
DRIVE OPTION
V
CC
-5V
DC