Philips Semiconductors

TDA8946AJ

2 x 15 W BTL audio amplifier with DC gain control

Product data

Rev. 01 — 01 March 2002

7 of 20

9397 750 09434

© Koninklijke Philips Electronics N.V. 2002. All rights reserved.

8.6 Built-in protection circuits

The TDA8946AJ contains two types of protection circuits, i.e. short-circuit and

thermal shutdown.

8.6.1

Short-circuit protection

Short-circuit to ground or supply line — This is detected by a so-called ‘missing

current’ detection circuit which measures the current in the positive supply line and

the current in the ground line. A difference between both currents larger than 0.8 A,

switches the power stage to the standby mode; high impedance of the outputs and

very low supply current.

Short-circuit across the load — This is detected by an absolute-current

measurement. An absolute-current larger than 2 A, switches the power stage to

standby mode; high impedance of the outputs and a very low supply current.

8.6.2

Thermal shutdown protection

The junction temperature is measured by a temperature sensor; at a junction

temperature of approximately 150

°C this detection circuit switches the power stage

to the standby mode; high impedance of the outputs and very low supply current.

9.

Limiting values

10. Thermal characteristics

[1]

This is a typical value.

Table 5:

Limiting values

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

Symbol

Parameter

Conditions

Min

Max

Unit

supply voltage

no signal

−0.3

+25

V

operating

−0.3

+18

V

input voltage

−0.3

V

repetitive peak output current

-

2

A

storage temperature

non-operating

−55

+150

°C

operating ambient temperature

−40

+85

°C

total power dissipation

-

28

W

supply voltage to guarantee short-circuit

protection

-15

V

Table 6:

Thermal characteristics

Symbol

Parameter

Conditions

Value

Unit

thermal resistance from junction to ambient

in free air

40

K/W

thermal resistance from junction to mounting base both channels driven

2.5[1]

K/W