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RC5042
PRODUCT SPECIFICATION
10
Design Considerations and
Component Selection
MOSFET Selection
This application requires N-channel
Logic Level
Enhance-
ment Mode Field Effect Transistors. Desired characteristics
are as follows:
Low Static Drain-Source On-Resistance,
R
DS(on)
< 37 m
W
(lower is better)
Low gate drive voltage, V
GS
< 4V
Power package with low thermal resistance
Drain current rating of 20A minimum
Drain-Source voltage > 15V.
The on-resistance (R
DS(ON)
) is the primary parameter for
MOSFET selection. The on-resistance determines the power
dissipation of the MOSFET and therefore significantly
affects the efficiency of the DC-DC Converter. Table 5 pre-
sents a list of suitable MOSFETs for this application.
Note:
1. R
DS(ON
) values at T
J
=125
°
C for most devices were extrapolated from the typical operating curves supplied by the
manufacturers and are approximations only. Only National Semiconductor offers maximum values at T
J
= 125
°
C.
Table 5. MOSFET Selection Table
Manufacturer & Model #
Fuji
2SK1388
Conditions
1
R
DS, ON
(m
W
)
Typ.
25
37
16.5
28
13
Package
TO-220
Thermal
Resistance
F
JA
= 75
Max.
37
—
20
34
15
V
GS
= 4V,
I
D
= 17.5A
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
Siliconix
SI4410DY
V
GS
= 4.5V,
I
D
= 5A
SO-8
(SMD)
F
JA
= 50
National Semiconductor
NDP706AL
NDP706AEL
National Semiconductor
NDP603AL
National Semiconductor
NDP606AL
Motorola
MTB75N03HDL
Int. Rectifier
IRLZ44
Int. Rectifier
IRL3103S
V
GS
= 5V,
I
D
= 40A
TO-220
F
JA
= 62.5
F
JC
= 1.5
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
T
J
= 25
°
C
T
J
= 125
°
C
20
31
42
22
33
6
9.3
—
—
—
24
40
54
25
40
9
14
28
46
19
31
V
GS
= 4.5V,
I
D
= 10A
TO-220
F
JA
= 62.5
F
JC
= 2.5
F
JA
= 62.5
F
JC
= 1.5
F
JA
= 62.5
F
JC
= 1.0
F
JA
= 62.5
F
JC
= 1.0
F
JA
= 62.5
F
JC
= 1.0
V
GS
= 5V,
I
D
= 24A
TO-220
V
GS
= 5V,
I
D
= 37.5A
TO-263
(D
2
PAK)
TO-220
V
GS
= 5V,
I
D
= 31A
V
GS
= 4.5V,
I
D
= 28A
TO-220