Datasheet

TDA7491HV Application information
Doc ID 14242 Rev 6 39/41
Using such a PCB with a copper ground layer of 3x3 cm
2
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 primarly 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 increase 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 59 shows the derating curves for copper areas of 4 cm
2
and 9 cm
2
.
Figure 59. Power derating curves for PCB used as heatsink
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120 140 160
g
Pd (W)
Tamb ( °C)
Copper Area 2x2 cm
and via holes
TDA7491P
PSSO36
Copper Area 3x3 cm
and via holes
TDA7491HV
PowerSSO-36