IRLR3715Z International Rectifier, IRLR3715Z Datasheet - Page 8

• Manufacturer Part Number: IRLR3715Z
• Description: MOSFET N-CH 20V 49A DPAK
• Manufacturer: International Rectifier
• Series: HEXFET®r

Specifications of IRLR3715Z

• Fet Type: MOSFET N-Channel, Metal Oxide
• Fet Feature: Logic Level Gate
• Rds On (max) @ Id, Vgs: 11 mOhm @ 15A, 10V
• Drain To Source Voltage (vdss): 20V
• Current - Continuous Drain (id) @ 25° C: 49A
• Vgs(th) (max) @ Id: 2.55V @ 250µA
• Gate Charge (qg) @ Vgs: 11nC @ 4.5V
• Input Capacitance (ciss) @ Vds: 810pF @ 10V
• Power - Max: 40W
• Mounting Type: Surface Mount
• Package / Case: DPak, TO-252 (2 leads+tab), SC-63
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *IRLR3715Z

Control FET
P
P
Power MOSFET Selection for Non-Isolated DC/DC Converters
loss
8
loss
This can be expanded and approximated by;
= I
+ I ×
+ Q
+
= P
(



(


Q
rms
conduction
g
2
oss
× V
2
Q
× R
i
× V
g
gd
g
× f
ds(on )
in
× V
+ P
× f
)
in
)
switching
× f



 + I ×

+ P



drive
Q
+ P
i
gs 2
g
× V
output
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
+ Q
+
(
(



conduction
rms
Q
oss
g
2
oss
2
× V
Characteristic
gd
× R
/Q
× V
g
gs1
+ P
ds(on)
× f
in
in
must be minimized to reduce the
. As Q1 turns on and off there is
drive
× f
)
)
rr


+ P
both generate losses that
+ Q
output
(
*
rr
× V
www.irf.com
in
ds(on)
× f
oss
is an im-
and re-
)