Thermal information

STA540

16/25

Doc ID 13907 Rev 6

5.1.3

Calculations using music power

The thermal resistance value calculated in each of the two above examples specifies a

heatsink capable of sustaining the maximum dissipated power. Realistically, however, and

as explained in the Application Note (AN1965), the heatsink can be smaller when the

application is musical content.

When music power is considered the resulting dissipation is about 40% less than the

calculated maximum. Thus, smaller or cheaper heatsinks can be employed. The heatsink

thermal resistance values are modified as follows:

for example 5.1.1: 10.5 W - 40% = 6.3 W, thus giving Rth_c-amb = 14° C/W,

for example 5.1.2: 21 W - 40% = 12.6 W, thus giving Rth_c-amb = 6° C/W.