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THERMAL SHUT-DOWN

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 the 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 temperatureincreases up to 150

°C, the thermalshut-down simply reduces

the power dissipation and the current consumption.

The maximum allowable power dissipation depends upon the size of the external heatsink (i.e. its thermal

resistance); fig. 32 shows this dissipable power as a function of ambient temperature for different thermal

resistance.

Figure 30. Output power

and drain current vs. case

temperature

Figure 31. Output power

and drain current vs. case

temperature

Figure 32. Maximum allo-

wable power dissipation

vs. ambient temperature

MOUNTING INSTRUCTION : See TDA1904

TDA1905