TDA8586 datasheet(8/24 Pages) PHILIPS

8 / 24 page

1999 Apr 08

Philips Semiconductors

Preliminary speciﬁcation

Power ampliﬁer with load detection and

auto BTL/SE selection

TDA8586

FUNCTIONAL DESCRIPTION

The TDA8586 is a multi-purpose power amplifier with four

amplifiers and 2 buffer stages, which can be connected in

the following configurations with high output power and

low distortion:

• Dual Bridge-Tied Load (BTL) amplifiers

• Quad Single-Ended (SE) amplifiers.

In the BTL mode of operation, the 2 buffer amplifiers act as

inverting amplifiers to complete the bridge across the

‘front’ amplifiers (OUT1 and OUT3) and the ‘rear’ outputs

(OUT2 and OUT4) enter a high-impedance state.

In the SE mode of operation, the buffers act as an AC

ground path thereby eliminating the need for series

capacitors on the speaker outputs.

Diagnostics:

• While the IC is in the mute mode, the diagnostic output

will signal the mode of operation when the IC is not

overruled

• In the on mode the diagnostic output will signal any fault

in the IC or if the output of any amplifier is clipping with

a distortion of 10% (or 2% depending on selected

clip-mode).

Special attention is given to the dynamic behaviour as

follows:

• Noise suppression during engine start

• No plops when switching from standby to on

• Slow offset change between mute and on (controlled by

MSO pin)

• Low noise levels, which are independent of the supply

voltage.

Protections are included to avoid the IC being damaged at:

• Over temperature: Tj > 150 °C

• Short-circuit of the output pin(s) to ground or supply rail.

When short-circuited, the power dissipation is limited

• ESD protection (Human Body Model 3000 V and

Machine Model 300 V).

The presence of the load is measured after the transition

between standby and mute. The IC will determine if there

is an acceptable load on both outputs (OUT2 and OUT4).

If both outputs are unloaded, the IC will switch to a

2 speaker mode of operation (BTL mode), unless it is

overruled.

There are two options to overrule:

1. Before transition from mute to on, after a load

detection, pulling the diagnostic output above 9.5 V

will force the IC into 4 speaker mode

2. TDA8586TH: pulling the OVERRULE pin according

pinning table.

Care should be taken with the OVERRULE function as it

works during the on mode. If there is a 2 or 4 speaker

mode change during the on mode a large ‘plop’ can be

heard on the speakers.

The ACREF input (common signal input) acts with the four

signal inputs (IN1 to IN4) to provide quasi differential

inputs. A capacitor must be connected to this pin of which

the ground pin should be connected to the ground at the

signal source (usually the ground at the audio signal

processor). This capacitor has a dual function. During the

speaker detection, the signal ground capacitor is used to

set the time constant of the measurement (and thus

determines the minimum required switch-on time).

The capacitor on the MSO pin allows the integrate function

to provide immunity to outside noises during load

detection.

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