TDA8571J/N2S,112 データシートの表示（PDF） - NXP Semiconductors.

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TDA8571J/N2S,112

4 × 40 W BTL quad car radio power amplifier

NXP Semiconductors. 

Philips Semiconductors

4 × 40 W BTL quad car radio power

amplifier

Product specification

TDA8571J

FUNCTIONAL DESCRIPTION

The TDA8571J contains four identical amplifiers which can

be used for bridge applications. The gain of each amplifier

is fixed at 34 dB.

Mode select switch (pin MODE)

• 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 IN1, IN2, IN3 and IN4. When switching

from standby to mute, the slope should be at least 18 V/s.

This can be realized by:

• Microprocessor control

• External timing circuit (see Fig.3).

Diagnostic output (pin VDIAG)

DYNAMIC DISTORTION DETECTOR (DDD)

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

dynamic distortion detector becomes active and pin VDIAG

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 VDIAG 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 VDIAG 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 VDIAG 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 VDIAG 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.

handbook, halfpa+geVP

10 kΩ

MODE

BZX79C/3.9V

47 µF

MGD959

Fig.3 Mode select switch circuitry.

handbook, halfpVagoe

0

MGG155

V9

VP

0

t

Fig.4 Distortion detector waveform.

2002 Mar 05

5

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