Datasheet

Product data sheet Rev. 03 — 20 March 2008 11 of 107

NXP Semiconductors

TEF6901A

Integrated car radio

In the weak signal processing block these signals are combined in speciﬁc ways and used

for the generation of control signals for soft mute, stereo blend (SNC = stereo noise

control) and HCC. Detector time constants of soft mute, HCC and SNC can be selected

independently.

In AM mode, soft mute and HCC are controlled by the average value of the level voltage.

7.26 Audio step interpolation

The tone/volume blocks of source selector, volume/balance, bass/loudness, fader and

output mute include the Audio Step Interpolation (ASI) function. This minimizes audible

pops by smoothing the transitions in the audio signal during the switching of the controls.

7.27 Source selector

The source selector selects one out of several input sources:

• One internal stereo signal (AM/FM tuner)

• Seven input pins allow many combinations of external sources by means of ﬂexible

input selection

Three of the seven input pins can connect to:

– 1 stereo signal with ground input for common mode rejection (CD)

– 1 stereo signal and 1 mono signal

Four more input pins can connect to:

– 1 stereo signal (AUX) and 1 mono signal with common mode rejection or

differential input (PHONE)

– 1 stereo signal (AUX) and 2 mono signals (e.g. NAV and BEEP)

– 2 stereo signals (AUX and AUX-2)

– 1 stereo signal with common mode rejection (CD-2) and 1 mono signal (e.g.

BEEP)

– 1 stereo signal with differential input (CD-symmetrical)

7.28 VU-meter read

The input audio level of external sources can read out via the I

C-bus. Audio level

information is available on a logarithmic scale. In radio mode the AM or FM modulation

index is available in the same way.

7.29 Volume and balance

The volume/balance control is used for volume setting and also for balance adjustment.

The control range of the volume/balance control is between +20 dB and −75 dB in steps

of 1 dB.

7.30 CD compression

Dynamic volume compression is available for external input sources. This option is

generally used for audio from CD or other digital formats to reduce the very high dynamic

range of these signals into a range suitable for the car environment.