Philips Semiconductors

TDA8947J

4-channel audio amplifier

Preliminary data

Rev. 01 — 06 February 2004

8 of 24

9397 750 10779

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

8.5 Built-in protection circuits

The TDA8947J contains two types of detection sensors: one measures local

temperatures of the power stages and one measures the global chip temperature. At

a local temperature of approximately 185

°C or a global temperature of approximately

150

°C, this detection circuit switches off the power stages for 2 ms. High impedance

of the outputs is the result. After this time period the power stages switch on

automatically and the detection will take place again; still a too high temperature

switches off the power stages immediately. This protects the TDA8947J against

shorts to ground, to the supply voltage and across the load, and against too high chip

temperatures.

The protection will only be activated when necessary, so even during a short-circuit

condition, a certain amount of (pulsed) current will still be flowing through the short,

just as much as the power stage can handle without exceeding the critical

temperature level.

9.

Limiting values

[1]

The amplifier can deliver output power with non clipping output signals into nominal loads as long as

the ratings of the IC are not exceeded.

10. Thermal characteristics

Table 6:

Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter

Conditions

Min

Max

Unit

supply voltage

operating

−0.3

+26

V

no (clipping) signal

[1]

−0.3

+28

V

input voltage

−0.3

repetitive peak output

current

-4

A

storage temperature

non-operating

−55

+150

°C

ambient temperature

−40

+85

°C

total power dissipation

-

69

W

supply voltage to guarantee

short-circuit protection

-24

V

Table 7:

Thermal characteristics

Symbol Parameter

Conditions

Value

Unit

thermal resistance from

junction to ambient

in free air

40

K/W

thermal resistance from

junction to case

all channels driven

1.3

K/W