Philips A02U AA Service Manual page 103

Circuit Descriptions, Abbreviation List, and IC Data Sheets
CVBS_out
Video Video
Video
output
IF
IF Processing
Selection
Video
Video
Source
Base
Selection
band
Sound
Sound
Sound IF
IF 2nd IF
Processing
Selection
Sound
Audio
low-IF
Base band
AM
Selection
Demod.
Audio
Audio
Output
Base
Selection
band
LR_out
Figure 9-7 MPIF block diagram
Some MPIF features:
•
IF Processing:
–
Amplifier, AGC.
–
Down mixer to base band.
–
Sound trap, low pass filter.
•
Video base band switching:
–
CVBS, Y/C.
–
RGB, YPbPr (1fH/2fH).
•
Audio base band switching.
•
Video and audio A/D conversion.
•
I2D formatter:
–
Data transfer to ADOC.
Vision IF
The video signal is demodulated by means of an alignment-
free PLL carrier regenerator with an internal VCO. This VCO is
calibrated by means of a digital control circuit, which uses an
external crystal frequency as reference. The frequency setting
for the various standards (33.4, 33.9, 38.0, 38.9, 45.75 and
58.75 MHz) is realized via the I2C bus.
The AFC output is generated by the digital control circuit of the
IF-PLL demodulator and can be read via the I2C bus.
The AGC-detector operates on top sync or top white level.
The MPIF IC has an integrated sound trap filter. The trap
frequencies can be switched via the I2C-bus.
Also, a group delay correction filter is integrated. The filter can
be switched between the PAL BG curve and a flat group delay
response characteristic. This has the advantage that in multi-
standard receivers the video SAW filter does not need to be
switchable (cost effective).
Sound IF
The MPIF has a separate sound IF input to enable Quasi Split
Sound (QSS) applications. The sound IF amplifier is similar to
the vision IF amplifier and has a gain control range of about 55
dB.
The AGC detector measures the SIF carrier levels (average
level of AM or FM carriers) and ensures a constant signal
amplitude for the AM demodulator and QSS mixer.
For applications without SIF SAW filter, the IC can also be used
in intercarrier mode. In this mode, the composite video signal
from the VIF amplifier is fed to the QSS mixer and converted to
the intercarrier frequency. AM sound demodulation is realized
in the analog domain with the QSS mixer.
Source Selection
The following selector parts can be identified:
•
CVBS/YC source selector. The video input selector
consists of four independent source selectors, that can
select between the CVBS signal coming from the IF part
and four external CVBS signals. Two of the external CVBS
inputs can also be used as YC input. One selector is used
for selection of the primary video channel. A second
selector selects the CVBS or YC signal for the secondary
channel. The third and fourth selectors are used for
Control Video Sound
Video
ADC
I2D
Multi-
I2D I2D
Link
plexer
Sound
IF ADC
Audio
Base band
ADC
I2C
I2C
Clocking
Interface
CL 36532058_065.eps
281003
A02U AA
selection of analog CVBS outputs A and B for SCART or
line output. The primary channel can be a CVBS or YC
signal. If an YC signal is selected for the secondary
channel or external CVBS outputs A or B, the luminance
and chrominance signals are added so that a CVBS signal
is obtained. The video identification circuit detects the
presence of a video signal on the CVBS_IF input (CVBS0).
The identification output can be read via I2C bus and is
normally used to detect transmitters during search tuning.
•
RGB/YPbPr source selector. The IC has two RGB inputs.
Both inputs can also be used as YPbPr input for connection
of video sources with an YPbPr output like a DVD player.
The RGB inputs can also be used for fast insertion of RGB
signals (for instance on screen display menu's) in the
primary CVBS signal. The fast insertion switch is located in
the digital video processor. The RGB signals are converted
to YUV before further processing. The YUV output signal is
digitized with the help of two A to D converters. The U and
V components have half the bandwidth of the Y signal,
because the U and V signals are multiplexed and digitized
with the help of one A to D converter.
9. EN 103