FAN7393 Fairchild Semiconductor, FAN7393 Datasheet - Page 16

• Manufacturer Part Number: FAN7393
• Description: Half-bridge Gate Drive Ic
• Manufacturer: Fairchild Semiconductor

FAN7393 • Rev. 1.0.0
© 2009 Fairchild Semiconductor Corporation
The FAN7393 has a negative V
curve, as shown in Figure 48.
Even though the FAN7393 has been shown able to han-
dle these negative V
recommended that the circuit designer limit the negative
V
to minimize the value of parasitic elements and compo-
nent use. The amplitude of negative V
portional to the parasitic inductances and the turn-off
speed, di/dt, of the switching device.
General Guidelines
Printed Circuit Board Layout
The layout recommended for minimized parasitic ele-
ments is as follows:
S
Direct tracks between switches with no loops or devia-
tion.
Avoid interconnect links. These can add significant
inductance.
Reduce the effect of lead-inductance by lowering
package height above the PCB.
Consider co-locating both power switches to reduce
track length.
To minimize noise coupling, the ground plane should
not be placed under or near the high-voltage floating
side.
To reduce the EM coupling and improve the power
switch turn-on/off performance, the gate drive loops
must be reduced as much as possible.
Figure 48. Negative V
transient as much as possible by careful PCB layout
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
0
100
200
300
S
transient conditions, it is strongly
Pulse Width [ns]
400
S
Transient Characteristic
500
S
600
transient performance
700
S
voltage is pro-
800
900 1000
16
Placement of Components
The recommended selection of component is as follows:
It is strongly recommended that the placement of compo-
nents is as follows:
Place a bypass capacitor between the V
pins. A ceramic 1µF capacitor is suitable for most
applications. This component should be placed as
close as possible to the pins to reduce parasitic ele-
ments.
The bypass capacitor from V
the low-side driver and bootstrap capacitor recharge.
A value at least ten times higher than the bootstrap
capacitor is recommended.
The bootstrap resistor, R
sizing the bootstrap resistance and the current devel-
oped during initial bootstrap charge. If the resistor is
needed in series with the bootstrap diode, verify that
V
use is typically 5 ~ 10Ω, which increases the V
constant. If the voltage drop of the bootstrap resistor
and diode is too high or the circuit topology does not
allow a sufficient charging time, a fast recovery or
ultra-fast recovery diode can be used.
The bootstrap capacitor, C
capacitor, such as a ceramic capacitor.
Place components tied to the floating voltage pins (V
and V
the device and the FAN7393. NC (not connected) pins
in this package maximize the distance between the
high-voltage and low-voltage pins (see Figure 3).
Place and route for bypass capacitors and gate resis-
tors as close as possible to gate drive IC.
Locate the bootstrap diode, D
ble to bootstrap capacitor, C
The bootstrap diode must use a lower forward voltage
drop and minimal switching time as soon as possible
for fast recovery or ultra-fast diode.
B
does not fall below COM (ground). Recommended
S
) near the respective high-voltage portions of
BOOT
BOOT
BOOT
DD
, must be considered in
BOOT
, uses a low-ESR
to COM supports both
.
, as close as possi-
DD
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and V
BS
time
SS
B