SC1403ITSTRT View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SC1403ITSTRT' PDF : 31 Pages View PDF
POWER MANAGEMENT
AApppplliiccaattiioonnss IInnffoorrmmaattiioonn (Cont.)
PGATE = 1 ⋅ CG ⋅ V2 ⋅ fS
2
Cg is the effective gate capacitance, equal to the Total Gate Charge
divided by VGS from the vendor datasheet, and is 7.9nF for the
IRF7413. V in the above formula is the final gate-source voltage
on the mosfet, 5V for the SC1403.
The total mosfet losses is the sum of the three loss components.
P TOTAL _ DISS = PCONDUCTION + PSWITCHING + PGATE
The mosfet dissipation under conditions of 15V input, 6A load,
and ambient temperature of 25C, can be determined as:
DNOM = 0.22 ∆IL = 1.26A
IMIN = 5.37A IMAX = 6.63A IRMS = 4.88A
Rds(on) (100C) = 18 mohm
PCONDUCTION = 429mW
.
PSWITCHING = 97mW
PGATE = 30mW
PTOTAL_DISS = 429 + 97 + 30 = 556 mW
The junction temperature rise resulting from the power dissipation
is calculated as:
∆ TJ = P T ⋅ θ JA
PT is the total device dissipation, and θJA is the package thermal
resistance, which is 50°C/W for the IRf7413. The junction tem-
perature rise is then:
∆TJ = 0.556W . 50°C/W = 27.8°
This is a modest temperature rise, so no special heat sinking is
required when laying out the mosfet.
SC1403
2004 Semtech Corp.
13
United States Patent No. 6,377,032
www.semtech.com
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