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APPLICATION NOTE AN50
7
MOSFET Selection Cosiderations
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 mΩ (lower is better)
• Low gate drive voltage, V
GS
≤ 4.5V
• 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. It determines the power dissipation
within the MOSFET and, therefore, significantly affects the
efficiency of the DC-DC converter. Table 5 is a selection
table for MOSFETs.
Note:
1. R
DS,ON
values at Tj = 125°C for most devices were extrapolated from the typical operating curves supplied by the
manufacturers and are approximations only.
Table 3. MOSFET Selection Table
Manufacturer & Model # Conditions
1
R
DS, ON
(mΩ)
P ackage
Thermal
ResistanceTyp. Max.
Fuji
2SK1388
V
GS
= 4V, I
D
= 17.5A T
J
= 25°C 25 37 TO-220 Φ
JA
= 75
T
J
= 125°C 37 —
Siliconix
SI4410DY
V
GS
= 4.5V, I
D
= 5A T
J
= 25°C 16.5 20 SO-8
(SMD)
Φ
JA
= 50
T
J
= 125°C 28 34
National Semiconductor
NDP706AL
V
GS
= 5V, I
D
= 40A T
J
= 25°C 13 15 TO-220 Φ
JA
= 62.5
Φ
JC
= 1.5
NDP706AEL T
J
= 125°C 20 24
National Semiconductor V
GS
= 4.5V, I
D
= 10A T
J
= 25°C 31 40 TO-220 Φ
JA
= 62.5
NDP603AL T
J
= 125°C 42 54 Φ
JC
= 2.5
National Semiconductor V
GS
= 5V, I
D
= 24A T
J
= 25°C 22 25 TO-220 Φ
JA
= 62.5
NDP606AL T
J
= 125°C 33 40 Φ
JC
= 1.5
Motorola V
GS
= 5V, I
D
= 37.5A T
J
= 25°C 6 9 TO-263 Φ
JA
= 62.5
MTB75N03HDL T
J
= 125°C 9.3 14 (D
2
PAK) Φ
JC
= 1.0
Int. Rectifier V
GS
= 5V, I
D
= 31A T
J
= 25°C — 28 TO-220 Φ
JA
= 62.5
IRLZ44 T
J
= 125°C — 46 Φ
JC
= 1.0
Int. Rectifier V
GS
= 4.5V, I
D
= 28A T
J
= 25°C — 19 TO-220 Φ
JA
= 62.5
IRL3103S T
J
= 125°C — 31 Φ
JC
= 1.0
Intl Rectifier V
GS
= 4.5V,
I
D
= 3.7A
T
A
= 25°C 18 SO-8 Φ
JA
= 50
IRF7413 SMD