2003 Oct 21 10
Philips Semiconductors Product specification
Car radio integrated signal processor TEF6890H
7.6 Tone/volume control
The tone/volume control part consists of the following
stages:
• Input selector
• Loudness control
• Volume/balance control with muting
• Treble control
• Bass control
• Fader and output mute
• Beep generator
• NAV input
• Output mixer.
The settings of all stages are controlled via the I
2
C-bus.
The stages input selector, loudness, volume/balance,
bass, and fader/output mute include the Audio Step
Interpolation (ASI) function. This minimizes pops by
smoothing the transitions in the audio signal during the
switching of the controls. The transition time of the ASI
function is programmable by I
2
C-bus in four steps.
7.6.1 INPUT SELECTOR
The input selector selects one of four input sources:
• Two external stereo inputs (CD and TAPE)
• One external mono input (PHONE)
• One internal stereo input (AM/FM).
7.6.2 LOUDNESS
The output of the input selector is fed into the loudness
circuit. Four different loudness curves can be selected via
the I
2
C-bus. The control range is between 0 and −20 dB
with a step size of 1 dB; see Figs 16 to 19.
7.6.3 VOLUME/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 and −59 dB in
steps of 1 dB.
The combination of loudness and volume/balance realizes
an overall control range of +20 to −79 dB.
7.6.4 TREBLE
The signal is then fed to the treble control stage. The
control range is between +14 and −14 dB in steps of 2 dB.
Figure 20 shows the control characteristic. Four different
filter frequencies can be selected.
7.6.5 BASS
The characteristic of the bass attenuation curves can be
set to shelve or band-pass. Four different frequencies can
be selected as centre frequency of the band-pass curve.
Figures 21 and 22 show the bass curves with a band-pass
filter frequency of 60 Hz. The control range is between
+14 and −14 dB in steps of 2 dB.
7.6.6 FADER/MUTE
The four fader/mute blocks are located at the end of the
tone/volume chain. The control range of these attenuators
is 0 to −59 dB. The step size is:
• 1 dB between 0 and −15 dB
• 2.5 dB between −15 and −45 dB
• 3 dB between −45 and −51 dB
• 4 dB between −51 and −59 dB.
7.6.7 BEEP GENERATOR AND NAV INPUT WITH OUTPUT
MIXER
The output mixer circuit can add an additional audio signal
to any of the four outputs together with the main signal or
instead of the main signal.
The additional signal can be generated internally by the
beep generator with four different audio frequencies or
applied to the NAV input, for instance a navigation voice
signal.
7.7 RDS demodulator
The RDS demodulator recovers and regenerates the
continuously transmitted RDS or RBDS data stream of the
multiplex signal (MPXRDS) and provides the signals clock
(RDCL), data (RDDA) and quality (RDQ) for external use.
The RDS demodulator uses the reference frequency
(75.4 kHz) from the tuner IC and does not need a crystal.
