TDA9875A Philips Semiconductors, TDA9875A Datasheet - Page 14

• Manufacturer Part Number: TDA9875A
• Description: Digital TV Sound Processor DTVSP
• Manufacturer: Philips Semiconductors

Philips Semiconductors
6.2.1
All input channels to the digital crossbar switch (except for
the loudspeaker feedback path) are equipped with a level
adjust facility to change the signal level in a range from
+15 to 15 dB (see Fig.5). It is recommended to scale all
input channels to be 15 dB below full-scale ( 15 dB
full-scale) under nominal conditions.
6.2.2
The NICAM path has a switchable J17 de-emphasis.
6.2.3
A high-pass filter suppresses DC offsets from the
FM demodulator due to carrier frequency offsets and
supplies the monitor/peak function with DC values and an
unfiltered signal, e.g. for the purpose of carrier detection.
The de-emphasis function offers fixed settings for the
supported standards (50, 60 or 75 s and J17).
An adaptive de-emphasis is available for
Wegener-Panda 1 encoded programs.
A matrix performs the dematrixing of the A2 stereo, dual
and mono signals.
6.2.4
If NICAM B/G, I or D/K is received, the auto-mute is
enabled and the signal quality becomes poor, the digital
crossbar switch switches automatically to FM and
switches the matrix to channel 1. The automatic switching
depends on the NICAM bit error rate.
The auto-mute function can be disabled via the I
For NICAM L applications, it is recommended to
demodulate AM sound in the first sound IF and connect the
audio signal to the mono input of the TDA9875A.
By setting bit AMSEL (see Section 10.3.11), the
auto-mute function will switch to the audio ADC instead of
switching to the first sound carrier. The ADC source
selector bits (see Section 10.3.20) should be set to mono
input, where the AM sound signal should be connected.
6.2.5
This function provides data words from a number of
locations in the signal processing paths to the I
interface (2 data bytes). Signal sources include the
FM demodulator outputs, most inputs to the digital
crossbar switch and the outputs of the ADC. Source
selection and data read-out is performed via the I
1999 Dec 20
Digital TV Sound Processor (DTVSP)
L
NICAM
FM (AM)
NICAM
M
EVEL SCALING
ONITOR
PATH
AUTO
PATH
-
MUTE
2
C-bus
2
2
C-bus.
C-bus.
14
Optionally, the peak value can be measured instead of
simply taking samples. The internally stored peak value is
reset to zero when the data is read via the I
The monitor function may be used, for example, for signal
level measurements or carrier detection.
6.2.6
The matrix provides the following functions: forced mono,
stereo, channel swap, channel 1, channel 2 and spatial
effects.
There are fixed coefficient sets for spatial settings of 30%,
40% and 52%.
The Automatic Volume Level (AVL) function provides a
constant output level of 23 dB (full-scale) for input levels
between 0 and 29 dB (full-scale). There are some fixed
decay time constants to choose from, i.e. 2, 4 and 8 s.
Pseudo stereo is based on a phase shift in one channel via
a second-order all-pass filter. There are fixed coefficient
sets to provide 90 degrees phase shift at frequencies of
150, 200 and 300 Hz.
Volume is controlled individually for each channel ranging
from +24 to 83 dB with 1 dB resolution. There is also a
mute position. For the purpose of a simple control software
in the microcontroller, the decimal number that is sent as
an I
volume setting in dB (e.g. the I
the new volume value to +10 dB).
Balance can be realized by independent control of the left
and right channel volume settings.
Contour is adjustable between 0 and +18 dB with 1 dB
resolution. This function is linked to the volume setting by
means of microcontroller software.
Bass is adjustable between +15 and 12 dB with 1 dB
resolution and treble is adjustable between
+12 and 12 dB with 1 dB resolution.
For the purpose of a simple control software in the
microcontroller, the decimal number that is sent as an
I
the new contour, bass or treble setting in dB (e.g. the
I
Extra bass boost is provided up to 20 dB with 2 dB
resolution. The implemented coefficient set serves merely
as an example on how to use this filter.
The beeper provides tones in a range from approximately
400 Hz to 30 kHz. The frequency can be selected via the
I
loudspeaker and headphone channel signals.
2
2
2
C-bus data byte for contour, bass or treble is identical to
C-bus data byte +8 sets the new value to +8 dB).
C-bus. The beeper output signal is added to the
2
C-bus data byte for volume control is identical to the
L
OUDSPEAKER
(M
AIN
)
CHANNEL
2
C-bus data byte +10 sets
Product specification
TDA9875A
2
C-bus.