PNX3000 데이터 시트보기 (PDF) - Philips Electronics
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PNX3000 Datasheet PDF : 51 Pages
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Philips Semiconductors
Analog front end for digital video
processors
Preliminary specification
PNX3000
separate SAW or ceramic filter to the DTV input of the
PNX3000. The reason is that the selectivity of a SAW filter
for TV sound is not sufficient for FM radio and, if the SIF
input is used, no tuner AGC information is available.
For high performance FM radio it is recommended that a
10.7 MHz FM radio IF signal is supplied to the external
2nd SIF input. In this case the IF signal must be filtered by
an external bandpass filter, that also functions as an
anti-alias filter. The low-pass filter before the 2nd SIF ADC
must be bypassed by setting bus bit SLPM.
The IC includes a separate AGC circuit for the 2nd SIF
signal. This AGC is needed for intercarrier sound
applications and when an external sound IF signal is
supplied to the 2nd SIF input. The AGC amplifier is
preceded by a second order high-pass filter for
suppression of video signal components. The AGC time
constant is determined by an external capacitor.
7.4 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 to select the signal for 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 to select analog outputs
CVBS A and B, which can be used for SCART or line
output.
The primary channel can be a CVBS or YC signal. If a
YC signal is selected for the secondary channel or for the
external CVBS outputs A or B, the luminance and
chrominance signals are added to obtain a CVBS signal.
The IC has an extra YC input for connection of a 3D comb
filter. The comb signal can only be selected for the primary
video channel. The input pin CVBS_DTV allows an analog
CVBS signal derived from a digital broadcast (MPEG)
signal to be recorded with an analog VCR. This signal
cannot be selected for the primary video channel.
The video identification circuit detects the presence of a
video signal on the CVBS_IF input (pin CVBS0). The
identification output is normally used to detect transmitters
during search tuning and can be read via the I2C-bus. The
circuit can also be used to monitor the selected primary
CVBS or YC signal. Either mode is selected by bit VIM.
7.5 RGB/YPbPr source selector
The IC has two RGB inputs. Both inputs can also be used
as YPbPr input for connecting 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 menus) 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 by two
ADCs. The U and V components have half the bandwidth
of the Y signal, therefore the U and V signals are
multiplexed and digitized by one ADC.
7.6 Video ADCs and anti-alias filters
The PNX3000 contains four video ADCs for analog and
digital video broadcast signals. The clock frequency for the
ADCs is either 27 MHz or 54 MHz. Two analog signals can
be multiplexed at the input of one ADC. Then the clock
frequency of the ADC is 54 MHz and the sample frequency
of each channel is 27 MHz.
The video ADCs are 10-bit folding ADCs. The sample
frequency for standard 1fH video signals is 27 MHz. For
the YUV channel the sample frequency of the U and V
components is half the sample frequency of the Y signal.
For 2fH YPbPr or RGB input signals (for instance 480p or
1080i ATSC signals), the frequency that is used to sample
the YUV signals is twice as high as for 1fH signals. The
sample frequency is 54 MHz for Y and 27 MHz for
U and V. The high sample frequency requires two data
links to transport the video data to the digital video
processor.
The anti-alias filters before the ADCs limit the signal
bandwidth to prevent aliasing effects. The filters for YUV
can be bypassed by means of two separate bits: bit BPY
for the Y filter and bit BPUV for the U and V filters. This
enables the use of external anti-alias filters with increased
bandwidth for 2fH, RGB or YPbPr input signals.
Table 1 shows the signal bandwidths and sample rates for
the various types of video signals. Table 2 shows which
video signals are sent to the digital video processor for
both data link modes.
2004 Oct 04
12
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