Thermal shutdown

TDA2050

12/18

Doc ID 1461 Rev 3

6

Thermal shutdown

The presence of a thermal limiting circuit offers the following advantages:

1.

An overload on the output (even if it is permanent), or an above-limit ambient

temperature can be easily tolerated since Tj cannot be higher than 150 °C.

2.

The heatsink can have a smaller factor of safety compared with that of a conventional

circuit. There is no possibility of device damage due to high junction temperature. If for

any reason, the junction temperature increases up to 150 °C, the thermal shutdown

simply reduces the power dissipation and the current consumption.

The maximum allowable power dissipation depends upon the thermal resistance junction-

ambient. Figure 20 shows this dissipable power as a function of ambient temperature for

different thermal resistances.

Figure 20.

Maximum allowable power dissipation vs. ambient temperature

6.1

Mounting instructions

The power dissipated in the circuit must be removed by adding an external heatsink. Thanks

to the pentawatt package, the heatsink mounting operation is very simple, a screw or a

compression spring (clip) being sufficient. Between the heatsink and the package it is better

to insert a layer of silicon grease, to optimize the thermal contact; no electrical isolation is

needed between the two surfaces. Figure 21 shows an example of a heatsink.