FDMF6706B Fairchild Semiconductor, FDMF6706B Datasheet - Page 15

• Manufacturer Part Number: FDMF6706B
• Manufacturer: Fairchild Semiconductor

© 2011 Fairchild Semiconductor Corporation
FDMF6706B • Rev. 1.0.1
Application Information
Supply Capacitor Selection
For the supply inputs (VDRV & VCIN), a local ceramic
bypass capacitor is required to reduce noise and to
supply peak transient currents during gate drive
switching action. It is recommended to use a minimum
capacitor value of 1µF X7R or X5R. Keep this capacitor
close to the VCIN and VDRV pins and connect it to the
GND plane with vias.
Bootstrap Circuit
The bootstrap circuit uses a charge storage capacitor
(C
X7R or X5R capacitor is typically adequate. A series
bootstrap
applications to improve switching noise immunity. The
boot resistor (R
near the maximum rated V
controlling the high-side MOSFET turn-on slew rate and
VSHW overshoot. Typical R
2.0W are effective in reducing VSWH overshoot.
BOOT
), as shown in Figure 28. A capacitance of 100nF
resistor
PWM
Input
OFF
Open-
Drain
Output
Open-
Drain
Output
BOOT
PWM
Input
OFF
DISB
DISB
V
V
5V
5V
ON
ON
) may be required when operating
may
A
I
5V
A
I
5V
be
BOOT
IN
C
VDRV
needed
C
VDR
and is effective at
Figure 27.
values from 0.5 to
ZCD_EN#
DISB#
THWN
PWM
ZCD_EN#
DISB#
THWN
PWM
Figure 28.
VDRV
FDMF6706B
VDRV
CGND
FDMF6705
FDMF6706B
for
CGND
FDMF6705
R
VCIN
VCIN
specific
Block Diagram With V
VCIN
PGND
Power Loss Measurement
PGND
VIN
PHASE
C
VSWH
BOOT
VCIN
15
PHASE
VSWH
BOOT
VIN
R
VCIN Filter
The VDRV pin provides power to the gate drive of the
high-side and low-side power MOSFETs. In most cases,
VDRV can be connected directly to VCIN, which
supplies power to the logic circuitry of the gate driver.
For additional noise immunity, an RC filter can be
inserted between VDRV and VCIN. Recommended
values of 10Ω (R
and 1µF (C
Power Loss and Efficiency
Measurement and Calculation
Refer to Figure 28 for power loss testing method. Power
loss calculations are:
P
P
P
P
P
EFF
EFF
BOOT
IN
SW
OUT
LOSS_MODULE
LOSS_BOARD
C
R
=(V
VIN
BOOT
=V
MODULE
BOARD
=V
V V
A
I
IN
IN
SW
C
C
OUT
VIN
BOOT
V V
x I
SW
=100 x P
C
x I
=100 x P
BOOT
IN
VCIN
x I
A
I
=P
IN
CIN
OUT
SW
) + (V
=P
V
OUT
L
IN
IN
OUT
) from VCIN to CGND, Figure 27.
Filter
IN
(W)
- P
L
VCIN
(W)
- P
OUT
5V
V
OUT
IN
OUT
SW
C
SW
x I
OUT
) placed between VDRV and VCIN
/P
/P
5V
C
(W)
(W)
IN
IN
OUT
) (W)
(%)
(%)
I
OUT
A
I
OUT
A
V
OUT
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