TDA1908 datasheet(10/12 Pages) STMICROELECTRONICS

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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 perma-

nent), or an abovelimit ambient temperature can

be easily supported 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 temperature in-

crease up to 150

°C, the thermal shut-down sim-

ply reduces the power dissipation and the

current consumption.

The maximum allowable power dissipation de-

pends upon the size of the external heatsink (i.e. its

thermal resistance); fig. 25 shows the dissipable

power as a function of ambient temperature for

different thermal resistance.

Figure 24. Output power

and drain current vs.

case temperature

Figure 25. Output power

and drain current vs.

case temperature

Fi g ur e 2 6. Max i mum

power dissipation vs.

ambient temperature

MOUNTING INSTRUCTIONS

The thermal power dissipated in the circuit may be

removed by soldering the tabs to a copper area on

the PC board (see Fig. 27).

During soldering, tab temperature must not exceed

260

°C and the soldering time must not be longer

than 12 seconds.

Figure 27. Mounding example

Fi gu re 2 8. M ax imu m

power dissipation and

thermal resistance vs.

side ” ”

TDA1908

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