IRF3717 International Rectifier, IRF3717 Datasheet - Page 8

• Manufacturer Part Number: IRF3717
• Description: MOSFET N-CH 20V 20A 8-SOIC
• Manufacturer: International Rectifier
• Series: HEXFET®r

Specifications of IRF3717

• Fet Type: MOSFET N-Channel, Metal Oxide
• Fet Feature: Logic Level Gate
• Rds On (max) @ Id, Vgs: 4.4 mOhm @ 20A, 10V
• Drain To Source Voltage (vdss): 20V
• Current - Continuous Drain (id) @ 25° C: 20A
• Vgs(th) (max) @ Id: 2.45V @ 250µA
• Gate Charge (qg) @ Vgs: 33nC @ 4.5V
• Input Capacitance (ciss) @ Vds: 2890pF @ 10V
• Power - Max: 2.5W
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *IRF3717

Control FET
P
P
Power MOSFET Selection for Non-Isolated DC/DC Converters
loss
8
loss
This can be expanded and approximated by;
= P
I
Q
I
Q
rms
conduction
g
2
oss
2
Q
i
V
g
gd
g
R
V
ds(on )
in
+ P
V
f
in
f
switching
f
+ P
I
drive
Q
+ P
i
gs 2
g
output
V
in
f
Synchronous FET
by;
*dissipated primarily in Q1.
portant characteristic; however, once again the im-
portance of gate charge must not be overlooked since
it impacts three critical areas. Under light load the
MOSFET must still be turned on and off by the con-
trol IC so the gate drive losses become much more
significant. Secondly, the output charge Q
verse recovery charge Q
are transfered to Q1 and increase the dissipation in
that device. Thirdly, gate charge will impact the
MOSFETs’ susceptibility to Cdv/dt turn on.
of the converter and therefore sees transitions be-
tween ground and V
a rate of change of drain voltage dV/dt which is ca-
pacitively coupled to the gate of Q2 and can induce
a voltage spike on the gate that is sufficient to turn
the MOSFET on, resulting in shoot-through current .
The ratio of Q
potential for Cdv/dt turn on.
Figure A: Q
P
P
loss
loss
The power loss equation for Q2 is approximated
For the synchronous MOSFET Q2, R
The drain of Q2 is connected to the switching node
P
I
conduction
Q
rms
Q
oss
g
2
oss
2
Characteristic
gd
/Q
V
R
g
gs1
V
ds(on)
in
must be minimized to reduce the
in
P
. As Q1 turns on and off there is
drive
f
f
rr
both generate losses that
P
output
*
Q
rr
www.irf.com
V
in
ds(on)
oss
is an im-
f
and re-