SA58637 Datasheet, PDF (12/22 Pages) NXP Semiconductors – 2 X 2.2 W BTL audio amplifier

NXP Semiconductors
SA58637
2 × 2.2 W BTL audio amplifier
14.3 Thermal behavior
The measured thermal performance of the HVQFN20 package is highly dependent on the
configuration and size of the heat spreader on the application demo board. Data may not
be comparable between different semiconductor manufacturers because the application
demo boards and test methods are not standardized. The thermal performance of a
package for a specific application may also differ from those presented here because the
configuration of the application boards copper heat spreader may be significantly different.
NXP Semiconductors uses FR-4 type application boards with 28.3 g (1 oz) copper traces
with solder coating.
The demo board (see Figure 16) has a 28.3 g (1 oz) copper heat spreader that runs under
the IC and provides a mounting pad to solder to the die attach paddle of the HVQFN20
package. The heat spreader is symmetrical and provides a heat spreader on both top and
bottom of the PCB. The heat spreader on top and bottom side of the demo board is
connected through 2 mm diameter plated through holes. Directly under the DAP (Die
Attach Paddle), the top and bottom side of the PCB are connected by four vias. The total
top and bottom heat spreader area is 64.5 mm² (10 in²).
The junction to ambient thermal resistance, R_th(j-a) = 22 K/W for the HVQFN20 package
when the exposed die attach paddle is soldered to a 32.3 mm² (5 in²) area of 28.3 g (1 oz)
copper heat spreader on the demo PCB. The maximum sine wave power dissipation for
T_amb = 25 °C is:
1_----5_---0_-2---–_2-----2_---5_{- = 5.7 W}
Thus, for T_amb = 60 °C the maximum total power dissipation is:
1_----5_---0_-2---–_2-----6_---0_{- = 4.1 W}
The power dissipation as a function of ambient temperature curve (Figure 11) shows the
power derating profiles with ambient temperature for three sizes of heat spreaders. For a
more modest heat spreader using a 32.3 mm² (5 in²) area on the top or bottom side of the
PCB, the R_th(j-a) is 31 K/W. When the package is not soldered to a heat spreader, the
R_th(j-a) increases to 60 K/W.
SA58637_1
Product data sheet
Rev. 01 — 25 February 2008
© NXP B.V. 2008. All rights reserved.
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