Datasheet

Not Recommended for New Designs
DRV8402
www.ti.com SLES222 –FEBRUARY 2009
R
θJA
is a system thermal resistance from junction to
ambient air. As such, it is a system parameter with
the following components:
• R
θJC
(the thermal resistance from junction to case,
or in this example the heat slug)
• Thermal grease thermal resistance
• Heat sink thermal resistance
The thermal grease thermal resistance can be
calculated from the exposed heat slug area and the
thermal grease manufacturer's area thermal
resistance (expressed in °C-in
2
/W or °C-mm
2
/W). The
approximate exposed heat slug size is as follows:
• DRV8402, 36-pin PSOP3 …… 0.124 in
2
(80 mm
2
)
The thermal resistance of thermal pads is considered
higher than a thin thermal grease layer. Thermal tape
has an even higher thermal resistance and should not
be used at all. Heat sink thermal resistance is
Figure 8. Application Diagram Example for Three
predicted by the heat sink vendor, modeled using a
Phase PMSM Operation
continuous flow dynamics (CFD) model, or measured.
Thus the system R
θJA
= R
θJC
+ thermal grease
THERMAL INFORMATION
resistance + heat sink resistance.
The thermally enhanced package provided with the
See the TI application report, IC Package Thermal
DRV8402 is designed to interface directly to heat sink
Metrics (SPRA953A), for more thermal information.
using a thermal interface compound, (e.g., Arctic
Silver, TIMTronics 413, Ceramic thermal compound,
etc.). The heat sink then absorbs heat from the ICs
and couples it to the local air.
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Product Folder Link(s): DRV8402