TDA8569Q datasheet(5/20 Pages) PHILIPS

5 / 20 page

1997 Mar 27

Philips Semiconductors

Preliminary speciﬁcation

× 25 W BTL quad car radio power

ampliﬁer

TDA8569Q

FUNCTIONAL DESCRIPTION

The TDA8569Q contains four identical amplifiers which

can be used for bridge applications. The gain of each

amplifier is fixed at 26 dB.

Mode select switch (pin 15)

• Standby: low supply current (<100 µA)

• Mute: input signal suppressed

• Operating: normal on condition.

Since this pin has a low input current (<80

µA), a low cost

supply switch can be applied.

To avoid switch-on plops, it is advised to keep the amplifier

in the mute mode during

≥150 ms (charging of the input

capacitors at pins 10, 11, 13 and 14).

This can be realized by:

• Microprocessor control

• External timing circuit (see Fig.3).

Diagnostic output (pin 9)

DYNAMIC DISTORTION DETECTOR (DDD)

At the onset of clipping of one or more output stages, the

dynamic distortion detector becomes active and pin 9

goes LOW. This information can be used to drive a sound

processor or DC volume control to attenuate the input

signal and so limit the distortion. The output level of pin 9

is independent of the number of channels that are clipping

(see Fig.4).

SHORT-CIRCUIT DIAGNOSTIC

When a short-circuit occurs at one or more outputs to

ground or to the supply voltage, the output stages are

switched off until the short-circuit is removed and the

device is switched on again, with a delay of approximately

10 ms after removal of the short-circuit. During this

short-circuit condition, pin 9 is continuously LOW.

When a short-circuit occurs across the load of one or more

channels, the output stages are switched off during

approximately 10 ms. After that time it is checked during

approximately 50

µs to determine whether the short-circuit

is still present.

Due to this duty cycle of 50

µs/10 ms the average current

consumption during this short-circuit condition is very low.

During this short-circuit condition, pin 9 is LOW for 10 ms

and HIGH for 50

µs (see Fig.5). The protection circuits of

all channels are coupled. This means that if a short-circuit

condition occurs in one of the channels, all channels are

switched off. Consequently, the power dissipation in any

short-circuit condition is very low.

TEMPERATURE PRE-WARNING

When the virtual junction temperature Tvj reaches 145 °C,

pin 9 goes LOW.

OPEN COLLECTOR OUTPUTS

The diagnostic pin has an open collector output, so more

devices can be tied together. An external pull-up resistor is

needed.

Fig.3 Mode select switch circuitry.

handbook, halfpage

100 k

Ω

MGA708

µF

10 k

Ω

10 k

Ω

mode

select

switch

Fig.4 Distortion detector waveform.

handbook, halfpage

MGG155

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