76131SK8 データシートの表示（PDF） - Intersil
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76131SK8 Datasheet PDF : 10 Pages
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HUF76131SK8
Thermal Resistance vs Mounting Pad Area
The maximum rated junction temperature TJMAX constrains
the maximum allowable device power dissipation PDmax in
an application. The application ambient temperature TA (oC)
and thermal impedance ZθJA (oC/W) must be reviewed to
ensure that TJMAX (oC) is never exceeded. Equation 1
mathematically represents the relationship.
PDMAX = (---T----J---M---Z---A-θ---X-J---A--–----T----A-----)
(EQ. 1)
Intersil provides thermal information to assist the designer’s
preliminary application evaluation. Precise determination of
PDMAX is complex and influenced by many factors:
1. PC heat sink area and location (top and bottom), copper
leads and mounting pad area.
2. Air Flow, board orientation and type.
3. Power pulse width and duty factor.
Figure 22 addresses these points by depicting RθJA values
vs. top copper (component side) heat sink area. The
measurements were performed in still air using a horizontally
positioned FR-4 board with 1oz copper after 1000 seconds
of steady state power.
Figure 22 also displays the two RθJA values listed in the
Electrical Specifications table. The two points were chosen
to graphically depict the compromise between copper board
area, thermal resistance and ultimately power dissipation.
Thermal resistance values corresponding to other
component side copper areas can be obtained from Figure
22 or by calculation using Equation 2. Area in Equation 2 is
the top copper area including the gate and source pads.
RθJA = 79.3 – 21.8 × ln (Area)
(EQ. 2)
250
RθJA = 79.3 - 21.8*ln(AREA)
200
177.3oC/W - 0.0115in2
143.4oC/W - 0.054in2
150
100
50
0.001
0.01
0.1
1.0
AREA, TOP COPPER AREA (in2)
IGURE 22. THERMAL RESISTANCE vs MOUNTING PAD AREA
Figure 22 provides the necessary information for steady
state junction temperature or power dissipation calculations.
Transient pulse applications are best studied using the
Intersil device SPICE thermal model.
7
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