TDA8591 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TDA8591

4 × 44W into 4 Ω or 4 × 75W into 2 Ω quad BTL car radio power amplifier

Philips Electronics 

Philips Semiconductors

4 × 44 W into 4 Ω or 4 × 75 W into 2 Ω

quad BTL car radio power amplifier

Preliminary specification

TDA8591J

14.1 Special attention for SMD input capacitors

When SMD capacitors are used as input capacitors, low

frequency noise can occur due to stress on the PCB. The

SMD capacitors can operate like small microphones with

sensitivity of 1⁄f. Special attention should be paid to this

issue when selecting SMD capacitors at the four inputs

(MKT capacitors are recommended).

14.2 Capacitors on outputs

The TDA8591J is optimized for a capacitor of 22 nF from

each output to ground for RF immunity and ESD. These

capacitors can be replaced by the capacitors on the

connector block.

14.3 EMC precautions

The TDA8591J has an all N-type DMOS output stage. The

main advantage of having the same type of power

transistors in the output stage is symmetrical behaviour for

positive and negative signals (sound quality).

A charge pump (DC to DC converter with capacitors only)

is used to generate a voltage above the battery voltage to

drive the high-side power. The clock frequency of the

charge pump (2.9 MHz) is chosen above the AM

frequency band. To prevent possible crosstalk in the FM

frequency band, a SIL pad can be used between the rear

of the TDA8591J and the heatsink. This SIL pad is an

electrical isolator and thermal conductor. It is advisable to

connect the power supply lines of the TDA8591J directly to

the power supply on the printed circuit board of the radio,

so that a one-point earth bonding with the tuner supply is

achieved.

The external capacitor of the charge pump (connected to

pin CP) filters and buffers the voltage generated internally.

The loop area of the capacitor connected to pins CP and

PGND2 should be kept as small as possible. For optimum

performance the capacitor used should have a good

frequency performance, for example an SMD ceramic

capacitor. See Figs 35 and 36 for a good PCB layout.

14.4 Offset detection

As shown in Fig.34, to obtain the DC offset information, an

output from each bridge is summed and filtered through

external 220 kΩ resistors and a 1 µF capacitor at

pin OFFCAP. The low frequency roll-off can be chosen

with the resistor/capacitor combination. Because of the

random phase of the DC offset voltage, the capacitor on

pin OFFCAP should not be a conventional electrolytic

capacitor as leakage current in this capacitor would cause

a shift in low frequency roll-off because of no pre-biasing.

If the offset detection is not used, pin OFFCAP can be

connected to ground, the external components (resistors

of 220 kΩ and 2 kΩ and the capacitor of 1µF) are not

needed and the circuit is as shown in Fig.33.

14.5 Channel selection

The following recommendation for a four channel

application is given on the basis of the results of the

channel separation measurements and the dissipation

spread within the package:

Front-left = OUT1

Rear-left = OUT2

Rear-right = OUT3

Front-right = OUT4.

14.6 Detection of short-circuits

Table 3 Detection of short-circuits in standby, mute and operating modes.

AMPLIFIER MODE

Standby

Mute (no output signal)

Operating (output signal present)

SHORT-CIRCUIT ACROSS LOAD

no diagnosis

the value of short-circuit that activates

diagnosis and protection depends on

the output offset voltage

diagnosis and active protection if

short-circuit <0.4 Ω

SHORT-CIRCUIT TO SUPPLY

OR GROUND

no diagnosis

no diagnosis and no active protection if

short-circuit >100 Ω

no diagnosis and no active protection if

short-circuit >100 Ω

2002 Jan 14

27

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