FDMF6707C Fairchild Semiconductor, FDMF6707C Datasheet - Page 14

• Manufacturer Part Number: FDMF6707C
• Manufacturer: Fairchild Semiconductor

© 2011 Fairchild Semiconductor Corporation
FDMF6707C • Rev. 1.0.1
Application Information
Supply Capacitor Selection
For the supply inputs (V
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
of 100nF X7R or X5R capacitor is typically adequate. A
series bootstrap resistor may be needed for specific
applications to improve switching noise immunity. The
boot resistor may be required when operating near the
maximum rated V
high-side MOSFET turn-on slew rate and V
overshoot. Typical R
effective in reducing V
BOOT
), as shown in Figure 27. A bootstrap capacitance
Drain
PWM
Input
OFF
Open -
Output
DISB
V
Input
PWM
5
ON
OFF
Open -
Drain
Output
DISB
V
IN
5V
ON
BOOT
and is effective at controlling the
SWH
DRV
A
I
5
values from 0.5Ω to 2.0Ω are
overshoot.
A
I
5
and V
C
VDR
C
SMOD#
DISB
THWN#
PWM
CIN
Figure 27.
VDRV
SMOD#
THWN#
DISB
PWM
Figure 28.
), a local ceramic
VDRV
CGND
FDMF6707C
VDRV
R
FDMF6707C
VCIN
CGND
FDM 67 5
VCIN
VCIN
Block Diagram With V
PGN
PGN
Power Loss Measurement
SHW
C
VIN
VCIN
PHASE
BOOT
VSWH
VIN
PHASE
VSWH
BOOT
14
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 would
be 10Ω (R
(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
R
BOOT
IN
SW
OUT
LOSS_MODULE
LOSS_BOARD
BOOT
VCIN
C
=(V
=V
VIN
MODULE
BOARD
C
=V
VIN
) from VCIN to CGND (see Figure 27).
V V
IN
SW
C
V V
A
I
OUT
IN
C
BOOT
x I
A
I
BOOT
IN
=100 x P
x I
SW
VCIN
SW
=100 x P
IN
x I
=P
CIN
OUT
) + (V
=P
) placed between VDRV and VCIN and 1µF
OUT
V
L
IN
L
Filter
IN
OUT
IN
V
OUT
(W)
- P
IN
(W)
- P
5V
OUT
OUT
SW
C
SW
C
x I
/P
OUT
OUT
/P
5V
(W)
(W)
IN
IN
) (W)
(%)
(%)
I
I
OUT
A
OUT
A
V
OUT
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