Datasheet

Package thermal characteristics STA333W
44/49 Doc ID 13365 Rev 2
9 Package thermal characteristics
A thermal resistance of 25 °C/W can be achieved by mounting the device on a PCB which
has two copper ground areas of 3 x 3 cm and 16 vias (see Figure 21).
Given that the amount of power dissipated within the device depends primarily on the supply
voltage, load impedance and output modulation level the maximum estimated dissipated
power for the STA333W is 3 W.
With the above suggested board as heatsink, a maximum junction temperature rise, ∆Tj, of
75 °C is possible. In consumer environments where 50 °C is the maximum ambient
temperature this provides some safety margin before the intervention of the thermal
protection (T
j
= 150 °C).
Figure 21. Double-layer PCB with two copper ground areas and 16 vias
Figure 22 shows the power derating curve for the PowerSSO-36 package on PCBs with
copper areas of 2 x 2 cm
2
and 3 x 3 cm
2
.
Figure 22. Power derating curve for PCB used as heatsink
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120 140 160
Pd (W)
Tamb ( °C)
Copper Area 2x2 cm
and via holes
STA333W
PSSO36
Copper Area 3x3 cm
and via holes
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120 140 160
0
1
2
3
4
5
6
7
8
0 20 40 60 80 100 120 140 160
Pd (W)
Tamb ( °C)
Copper Area 2x2 cm
and via holes
Copper Area 2x2 cm
and via holes
STA333W
PSSO36
STA333W
PSSO36
Copper Area 3x3 cm
and via holes
Copper Area 3x3 cm
and via holes
STA333W
PowerSSO-36