TDA7350A datasheet(15/22 Pages) STMICROELECTRONICS

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Load Dump Voltage Surge

The TDA 7350A has a circuit which enables it to

withstand a voltage pulse train on pin 9, of the

type shown in fig. 36.

If the supply voltage peaks to more than 40V,

then an LC filter must be inserted between the

supply and pin 9, in order to assure that the

pulses at pin 9 will be held within the limits

shown.

A suggested LC network is shown in fig. 35.

With this network, a train of pulses with amplitude

up to 120V and width of 2ms can be applied at

point A. This type of protection is ON when the

supply voltage (pulse or DC) exceeds 18V. For

this reason the maximum operating supply volt-

age is 18V.

Polarity Inversion

High current (up to 10A) can be handled by the

device with no damage for a longer period than

the blow-out time of a quick 2A fuse (normally

connected in series with the supply). This fea-

tures is added to avoid destruction, if during fitting

to the car, a mistake on the connection of the

supply is made.

Open Ground

When the radio is in the ON condition and the

ground is accidentally opened, a standard audio

amplifier will be damaged. On the TDA7350A pro-

tection diodes are included to avoid any damage.

DC Voltage

The maximum operating DC voltage for the

TDA7350A is 18V. However the device can with-

stand a DC voltage up to 28V with no damage.

This could occur during winter if two batteries are

series connected to crank the engine.

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 excessive ambient temperature

can be easily withstood.

2)the heatsink can have a smaller factor of

safety compared with that of a conventional

circuit. There is no device damage in the case

of excessive junction temperature: all hap-

pens is that Po (and therefore Ptot) and Id are

reduced.

The maximum allowable power dissipation de-

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

its thermal resistance); Fig. 37 shows the dissipa-

ble power as a function of ambient temperature

for different thermal resistance.

Loudspeaker Protection

The TDA7350A guarantees safe operations even

for the loudspeaker in case of accidental shortcir-

cuit.

Whenever a single OUT to GND, OUT to VS short

circuit occurs both the outputs are switched OFF

so limiting dangerous DC current flowing through

the loudspeaker.

Figure 35

Figure 36

Figure 37: Maximum Allowable Power

Dissipation vs. Ambient Temperature

Figure 38: Restart Circuit

TDA7350A

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