TDA7491HV datasheet(39/50 Pages) STMICROELECTRONICS

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8.9

Heatsink requirements

Due to the high efficiency of the class-D amplifier a 2-layer PCB can easily provide the heatsinking capability for

low to medium power outputs. Using such a PCB with a copper ground layer of 3x3 cm2 and 16 vias connecting it

to the contact area for the exposed pad, a thermal resistance, junction-to-ambient (in natural air convection), of 24

°C/W can be achieved.

The dissipated power within the device depends primarily on the supply voltage, load impedance and output

modulation level. With the TDA7491HV driving 2 x 8 Ω with a supply of 18 V then the device dissipation is

approximately 4 W that gives with the above mentioned PCB a junction temperature rise of about 90 °C.

With a musical program, the dissipated power is about 40% less than the above maximum value. This leads to

a junction temperature increase of around 60 °C. So even at the maximum recommended ambient temperature

there is a margin of safety before the maximum junction temperature is reached.

Figure below shows the derating curves for copper areas of 4 cm2 and 9 cm2.

Figure 59. Power derating curves for PCB used as heatsink

100

120

140

160

Pd (W)

Tamb ( °C)

Copper Area 2x2 cm

and via holes

TDA7491HV

PSSO-36

Copper Area 3x3 cm

and via holes

TDA7491HV

Heatsink requirements

DS5624 - Rev 10

page 39/50

TDA7491HV Datasheet(PDF) 39 Page - STMicroelectronics