Functions, pins and components description

TDA7571

16/21

Rs-P-L, Cs-P-L

Rs-N-R, Cs-N-R

Rs-P-R, Cs-P-R

Are in the direction to increase the dumping (point 1) and reduce the dv/dt (point 2).

The value of these components is also depending on the layout structure. With a reduction

of the parasitic inductance present in the P.C. board layout, in the region around the power

transistors, the value of these components can be reduced, giving advantage in terms of

THD, mainly at mid-high power levels, due to the reduction of the "dead zone".

The minimum suggested value of Rd-x-x is around 10 Ohm, while, is some cases, Rs-x-x

and Cs-x-x can be removed.

4.6

PLL

In case of the schematic shown in Figure 3, the internal oscillator is locked by a PLL circuit

at the Master Clock input frequency (MCLK).

The loop filter of this PLL is externally connected to the pin F (39). It consists in a lag-lead

filter (Cpll1, Rpll). The output resistance of the pin F is a 10K (typ) resistor.

The typical suggested values of Cpll1 and Rpll are the following:

Cpll1 = 10Kpf

Rpll = 1Kohm.

In some cases, in a system with few clock interactions and a good MCLK signal, a parallel

capacitor Cpll2 of 2.2nF-4.7nF can help to decrease the noise at the pin F.

With the PLL option, the A.C. output amplitude is not dependant by the resistor Rosc,

because the voltage across Rosc is defined by the PLL itself, Moreover, the output A.C.

voltage is independent also from the clock of the PCM signal (32kHz, 44.1kHz, 48kHz).

Vice versa, if the free running oscillation is selected, the output signal is dependant by the

Rosc value and from the input PCM frequency.

4.7

Dither

With the pins D1 (43) and D2 (44) 4 types of digital dithering is achievable:

Because of the recorded signals (music or speech) already contains some amount of noise,

the dithering is generally not needed.

For high quality signals, it is suggested do not use the cases 3 and 4, that can be useful only

in case of low resolution signals without noise added.

Table 7.

4 types of digital dithering

D1

D2

Dithering

1

00

Low

2

01

Mid-low

3

1

0

Mid-high

4

1

1

High