FAN3217TMX Fairchild Semiconductor, FAN3217TMX Datasheet - Page 14

• Manufacturer Part Number: FAN3217TMX
• Description: IC GATE DRIVER DUAL 2A 8-SOIC
• Manufacturer: Fairchild Semiconductor
• Type: Low Side Gate Driversr

Specifications of FAN3217TMX

• Product: MOSFET Gate Drivers
• Rise Time: 12 ns
• Fall Time: 9 ns
• Propagation Delay Time: 19 ns
• Supply Voltage (max): 18 V
• Supply Voltage (min): 4.5 V
• Supply Current: 0.75 mA
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8
• Minimum Operating Temperature: - 40 C
• Output Current: 2.4 A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

© 2009 Fairchild Semiconductor Corporation
FAN3216 / FAN3217 • Rev. 1.0.1
Thermal Guidelines
Gate drivers used to switch MOSFETs and IGBTs at
high frequencies can dissipate significant amounts of
power. It is important to determine the driver power
dissipation and the resulting junction temperature in the
application to ensure that the part is operating within
acceptable temperature limits.
The total power dissipation in a gate driver is the sum of
two components, P
Once the power dissipated in the driver is determined,
the driver junction rise with respect to circuit board can
be evaluated using the following thermal equation,
assuming 
design (heat sinking and air flow):
P
Gate Driving Loss: The most significant power loss
results from supplying gate current (charge per unit
time) to switch the load MOSFET on and off at the
switching frequency. The power dissipation that
results from driving a MOSFET at a specified gate-
source voltage, V
switching frequency, f
P
where n is the number of driver channels in use (1 or 2).
Dynamic Pre-Drive / Shoot-through Current: A power
loss resulting from internal current consumption under
dynamic operating conditions, including pin pull-up /
pull-down resistors, can be obtained using the graphs
in Typical Performance Characteristics to determine
the current I
operating conditions:
P
T
where:
T

T
J
J
B
TOTAL
GATE
DYNAMIC
JB
= Q
= P
= driver junction temperature;
= (psi) thermal characterization parameter
relating temperature rise to total power
dissipation; and
= board temperature in location as defined in
the Thermal Characteristics table.
= P
= I
G
TOTAL
GATE
JB
DYNAMIC
• V
was determined for a similar thermal
DYNAMIC
GS
+ P
• 
GATE
• f
DYNAMIC
JB
• V
SW
GS
+ T
and P
SW
drawn from V
DD
, with gate charge, Q
• n
, is determined by:
B
• n
DYNAMIC
:
DD
under actual
G
(1)
, at
(2)
(3)
(4)
14
In the forward converter with synchronous rectifier
shown
FDMS8660S is a reasonable MOSFET selection. The
gate charge for each SR MOSFET would be 60nC with
V
total power dissipation is:
The
characterization parameter of 
application, the localized temperature around the device
is a function of the layout and construction of the PCB
along with airflow across the surfaces. To ensure
reliable operation, the maximum junction temperature of
the device must be prevented from exceeding the
maximum rating of 150°C; with 80% derating, T
be limited to 120°C. Rearranging Equation 4 determines
the board temperature required to maintain the junction
temperature below 120°C:
GS
= V
P
P
P
T
T
GATE
DYNAMIC
TOTAL
B
B
SOIC-8
= T
= 120°C – 0.46W • 43°C/W = 100°C
DD
in
= 7V. At a switching frequency of 500kHz, the
= 60nC • 7V • 500kHz • 2 = 0.42W
J
= 0.46W
- P
the
= 3mA • 7V • 2 = 0.042W
TOTAL
has
typical
• 
JB
a
application
junction-to-board
JB
= 43°C/W. In a system
diagrams,
www.fairchildsemi.com
thermal
J
would
(5)
(6)
(7)
(8)
(9)
the