Philips A02E Service Manual page 71

Circuit Descriptions, Abbreviation List, and IC Data Sheets
signals from the audio ADCs of the MPIF IC. The SSIF needs
some hardware processing before it enters the DEMDEC DSP.
The DEMDEC processing will be described in the next chapter.
The audio signals from the audio ADCs of the MPIF are
passing the DEMDEC DSP only for source selection and
sample rate conversion.
In this chassis, two of the DAC outputs are used to feed a
headphone. Two other DAC stereo outputs are provided for the
audio feedback to the MPIF IC. They are located to pins of the
ADOC that suit best for connection to MPIF.
7300-x
ADOC SOUND & AUDIO PROCESSING
Demodulation and Decoding DSP
DDEP
Down
SSIF Preprocessing SRC
Mix
B5
EXT. STEREO
Decimation
Filter
EXT. MONO
I/P
Level
Audio Processing DSP
X-
Adj.
Bar
WS PLL
I2SIN I2SOUT
N.C. N.C.
7300-B
Figure 9-17 ADOC sound processing block diagram
DEMDEC DSP
The output signals of the above-mentioned hardware blocks,
plus four audio ADC channels are read in by the DEMDEC
DSP, processed, converted to the current audio sample rate,
"demultiplexed", and forwarded to the Audio DSP for further
processing (volume, tone control, effects etc.).
Down Mixer
The digitised SSIF input signal is fed to the mixers, which mix
one or both input sound carriers down to zero IF.
Pre-processing
This part contains the sound system identification and
demodulation circuitry.
Audio Sample Rate Conversion (SRC)
All input signals pass through a sample rate conversion to the
actual output sample rate (usually 48 kHz) such that the output
rate does not need to be synchronised with any of the input
rates. Up to five separate channels can be converted.
Audio Processing DSP
This block applies several filters, like down-sampling and de-
emphasis, noise reduction processing, performs a sample rate
conversion (SRC) to the current audio sample rate, and routes
the decoded signals to the output channels.
The generic processing controls are Volume, Bass, Treble,
Balance, Incredible Surround, Spatial (incredible mono), DBE,
Dynamic Ultra Bass II (for non-woofer sets only), AVL, Sub-
Woofer, and 5-band Graphic equaliser.
The Headphone volume can be separately controlled in the
Headphone menu without affecting the master volume (the
setting of the volume tables will be adapted after fine tuning).
For variable volume output for USA, the DAC1 output will
switch to the Main channel and therefore the same volume
curve for the Main Channel can be used.
VDDCO VDDE
Dematrix
and Select
AUD_SPK_R
AUD_SPK_L
AUD_SPK_SW
AUD_SPK_C
AUD_SPK_SL
O/P
X-
Bar AUD_HP_R
DAC
AUD_HP_L
DSNDR2
DSNDL2
DSNDR1
DSNDL1
CL 36532058_077.eps
281003
A02E
9.6.4
Audio Amplifier
Speakers (diagram A6)
The audio output stage is built around IC7701 , which is a
balanced amplifier, and is located on the LSP. It uses an
monolithic integrated power amplifier IC, the TDA7497. The
gain of the amplifier is constant. This means that volume
control is done via the ADOC.
The supply voltage is +28 V, generated by the power supply via
L5506 (or L5512). The TDA7497 delivers an output of 3 x 10
W_rms to two full range speakers and an (optional) subwoofer.
Muting
There are three types of muting available: system mute,
headphone status mute, and user mute.
•
System mute. System muting is implemented for "special
events" such as channel/source change event, loss of
identification signal, "on/off" switching of the set, during
search and auto store/program, and/or sound mode
change. This muting is transparent to the user. Audio
output is muted before the above "special events"
occurred, to prevent problems such as audible plop. Muting
is done via the SOUND-ENABLE (software controlled) and/
or POR (hardware controlled) line connected (via TS7710
and 7711) to pin 10 of the amplifier-IC and coming from the
ADOC microprocessor.
•
Headphone status mute. A headphone status is available
to detect the presence of the headphone and mute the
main speakers if the headphone is detected. The
microprocessor will read the FRONT-DETECT status.
•
User mute. This is a mute option available to the user. The
user select the MUTE option on the remote control to
switch "off/on" the sound output to the main loudspeaker
and the (optional) subwoofer.
Headphone amplifier (diagram A7)
The headphone amplifier is built around IC7751 (NJM4556),
which is a high-gain, high output current dual operational
amplifier. The supply voltage is +5 V.
9.7
Control
9.7.1
Introduction
The MIPS processor within the ADOC performs the control of
the complete SALSA system. This part of the document will
examine the functions that enable the MIPS to operate and
control the remainder of the SALSA system.
Some control features:
•
MIPS1910 processor (MIPS).
•
Embedded SRAM.
•
External Bus Interface Unit (EBIU) for external memory
access.
•
SDRAM Interface.
•
Interrupt Controller.
•
Power and Clock management.
•
General Purpose I/O (GPIO).
•
Analogue to Digital conversion.
•
Two x I2C master/slave.
•
Two x General Purpose Timers.
•
UART.
•
Two x Multi-standard VBI Data Capture Unit.
•
EJTAG (for debug and boundary scan functions).
•
Remote Control (Infra Red) pre-processing.
•
Graphics.
9. EN 103