AN3383

Design guidelines for schematic and PCB layout

Doc ID 018691 Rev 1

17/29

The snubber network allows the energy (big spike) to be transferred to and from the

snubber network in order for the system to be worked on safely.

2.

The purpose of the main filter is to limit the frequency higher than the audible range of

20 kHz, which is mandatory in order to have a clean amplifier response. The main filter

is designed using the Butterworth formula to define the cutoff frequency.

3.

The purpose of the damping network is to avoid the high-frequency oscillation issue on

the output circuit. The damping network allows the THD to be improved and also allows

avoiding the inductive copper on the PCB route when the system is working on high

frequency with PWM or PCM.

Snubber filter

The snubber circuit must be optimized for the specific application. Starting values are

330 pF in series to 22 ohm. The power on this network is dependent on the power supply,

frequency and capacitor value according to the following formula:

This power is dissipated over the series resistance as shown in Figure 22

Figure 22.

In the following case the formula to evaluate power is:

This power is dissipated over the series resistance as shown in Figure 23:

Figure 23.

C126

330p

R44

22

INxA

INxB

AM045251v1

C127

330p

C130

330p

R45

22

R46

22

INxA

INxB

AM045252v1