L6747A STMicroelectronics, L6747A Datasheet - Page 11

• Manufacturer Part Number: L6747A
• Description: High current MOSFET driver
• Manufacturer: STMicroelectronics

Specifications of L6747A

• Flexible Gate-drive: 5 V to 12 V compatible

L6747A
4.5
Referring to
stage with two different MOSFETs: a P-MOSFET to drive the external gate high, and an N-
MOSFET to drive the external gate low (with their own R
R
(C
MOSFET to reach the driving voltage (PVCC for HS and VCC for LS). This capacitor is
charged and discharged at the driver switching frequency F
The total power P
driving path. According to the external gate resistance and the power MOSFET intrinsic
gate resistance, the driver dissipates only a portion of P
The total power dissipated from the driver can then be determined as follows:
Figure 6.
Layout guidelines
The L6747A provides driving capability to implement high-current step-down DC-DC
converters.
The first priority when placing components for these applications should be given to the
power section, minimizing the length of each connection and loop as much as possible. To
minimize noise and voltage spikes (as well as EMI and losses) power connections must be
part of a power plane, and in any case constructed with wide and thick copper traces. The
loop must be minimized. The critical components, such as the power MOSFETs, must be
close to each other. However, some space between the power MOSFETs is required to
assure good thermal cooling and airflow.
P
P
P
lo_LS
SW HS
SW LS
G_HS
=
LS DRIVER
–
–
P
DC
). The external power MOSFET can be represented in this case as a capacitance
, C
=
+
=
G_LS
LGATE
P
1
-- - C
2
GND
VCC
1
-- - C
2
SW HS
Figure
⋅
Equivalent circuit for a MOSFET driver
⋅
) that stores the gate-charge (Q
–
GLS
GHS
SW
R
+
GATELS
6, a classic MOSFET driver can be represented by a push-pull output
⋅
⋅
VCC
PVCC
P
is dissipated among the resistive components distributed along the
LS MOSFET
SW LS
2
–
⋅
R
2
Fsw
ILS
C
⋅
GLS
Fsw
Doc ID 17126 Rev 1
⋅
⎛
⎝
⋅
------------------------------------------------------------- -
R
⎛
⎝
hiLS
--------------------------------------------------------------- -
R
hiHS
+
R
+
R
GateLS
R
hiLS
R
GateHS
hiHS
G_HS
+
R
, Q
+
iLS
R
G_LS
iHS
+
SW
Device description and operation
DS(on)
------------------------------------------------------------- -
R
HS DRIVER
+
loLS
) required by the external power
as follows:
SW
--------------------------------------------------------------- -
R
loHS
: R
.
+
HGATE
PHASE
R
BOOT
hi_HS,
VCC
R
+
GateLS
loLS
R
R
GateHS
loHS
R
R
+
lo_HS
GATEHS
R
iLS
+
HS MOSFET
, R
R
⎞
⎠
iHS
C
R
hi_LS,
GHS
IHS
⎞
⎠
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