SC1403_04 SEMTECH [Semtech Corporation], SC1403_04 Datasheet - Page 13

• Manufacturer Part Number: SC1403_04
• Description: Mobile Multi-Output PWM Controller with Lossless Current Sense
• Manufacturer: SEMTECH [Semtech Corporation]

Applications Information
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.
The mosfet dissipation under conditions of 15V input, 6A load,
and ambient temperature of 25C, can be determined as:
.
The junction temperature rise resulting from the power dissipation
is calculated as:
P
resistance, which is 50°C/W for the IRf7413. The junction tem-
perature rise is then:
This is a modest temperature rise, so no special heat sinking is
required when laying out the mosfet.
POWER MANAGEMENT
Applications Information (Cont.)
T
2004 Semtech Corp.
is the total device dissipation, and
P
TOTAL
DNOM = 0.22
IMIN = 5.37A
Rds(on) (100C) = 18 mohm
PCONDUCTION = 429mW
PSWITCHING = 97mW
PTOTAL_DISS = 429 + 97 + 30 = 556 mW
P
T
GATE
T
J
_
= 0.556W
J
DISS
1
2
P
C
T
G
P
θ
V
CONDUCTION
.
2
50°C/W = 27.8°
JA
IMAX = 6.63A
f
S
IL = 1.26A
P
JA
SWITCHING
is the package thermal
IRMS = 4.88A
PGATE = 30mW
P
GATE
13
United States Patent No. 6,377,032
www.semtech.com
SC1403