TDA7266P

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PCB LAYOUT AND EXTERNAL COMPONENTS

Regarding the PCB layout care must be taken for three main subjects:

1) Signal and Power Gnd separation

2) Dissipating Copper Area

3) Filter Capacitors positioning

1) Signal and Power Gnd separation:

To the Signal GND must be referred the Audio Input Signals, the Mute and Stand-by Voltages and the

device PIN.14. This Gnd path must be as clean as possible in order to improve the device THD+Noise

and to avoid spurious oscillations across the speakers.

The Power GND is directly connected to the Output power Stage transistors (Emitters) and is crossed

by large amount of current, this path is also used in this device to dissipate the heating generated (no

needs of external heatsinker).

Referring to the typical application circuit, the separation between the two GND paths must be obtained

connecting them separately (star routing) to the bulk

Electrolithic capacitor C1 (470

µF).

Regarding the Power Gnd dimensioning we have to consider the Dissipated Power the Thermal Pro-

tection Threshold and the Package thermal Characteristics.

2) Dissipating Copper Area:

Dissipated Power:

The max dissipated power happens for a THD near 1% and is given by the formula:

This gives for: Vcc = 7.5V, Rl = 8

Ω ,Iq = 40mA a dissipated power of Pd = 3W.

Thermal Protection:

The thermal protection threshold is placed at a junction temperature of 150°C.

Package Thermal Characteristics:

The thermal resistance Junction to Ambient obtainable with a GND copper Area of 3x3 cm and with 16 via

holes (see picture) is about 25°C/W. This means that with the above mentioned max dissipated Power

(Pd=3W) we can expect a 75°C, this gives a safety margin before the thermal protection intervention in the

consumer environments where a 50°C ambient is specified as maximum

Figure 11.

3)Filter Capacitors Positioning:

The two Ceramic capacitors C2/C7 (100nF) must be placed as close as possible

respectively to the two Vcc pins ( 7 - 18) in order to avoid the possibiltiy of oscillations arising on the

output Audio signals.

P

dm ax W

()

2

V

CC

2

π

2

Rl

2

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I

+

⋅

=