TDA4350X Datasheet, PDF (5/32 Pages) Siemens Semiconductor Group – Audioprocessor

TDA 4350X
2
Circuit Description
2.1 Signalprocessing
1. The selection of the AF inputs happens in the input switch. There are three
stereo-inputs available. One of the input pairs is equipped with a separate floating
ground connection especially provided for external signal sources. Crosstalk to this
input is suppressed by common mode rejection. An input level control circuitry behind
input switch realizes the adaption of different signal source levels. The circuit offers a
control range from 0 dB to + 25 dB with a stepwidth of 2.5 dB. An I²C Bus controlled
first clipping detector allows a software controlled level adaption.
2. Next stage in signal path is volume control, with common setting for both channels, a
control range of 0 dB to – 78.75 dB and a stepwidth of 1.25 dB. In this stage a
loudness function is realized. A loudness control circuit, in fact a second volume
control circuit with identical structure, is to be set to a higher level as volume control.
The resulting level difference fixes the maximum amplitude response of the loudness
function. The frequency response, only bass boost or combined bass and treble boost
is fixed by external components. Because the volume and loudness control are strictly
independent of each other, the frequency response and threshold of the loudness
function is programmable via software. A switch bit allows to enable the loudness
function easily. Some possible loudness setups:
Loudness function starting at max.
vol. then ∆ continuously increasing.
Figure 3
Semiconductor Group
5
04.96