SAA4963T Philips, SAA4963T Datasheet - Page 6

• Manufacturer Part Number: SAA4963T
• Description: Integrated NTSC comb filter
• Manufacturer: Philips

Philips Semiconductors
CSY (
Sync top capacitor for the sync separator.
CVBS (
Input for the CVBS signal in COMB-mode.
Y
Input for an external luminance signal in SVHS-mode.
REFBP (
Decoupling capacitor for the band-pass filter reference
voltage.
Internal functional description
S
Delays the CVBS input signal by 1 line. Input signals for
the delay lines are the CVBS signal, the clock CL3 (3
and the control signal HSEL.
Output signals are the non-delayed and the 1-line delayed
CVBS signal.
S
The comb filter input BPFs attenuate the low frequencies
to guarantee a correct signal processing within the
comb filter.
The comb filter output BPF reduces the alias components
that are the result of the signal processing within the
comb filter.
C
Separates the chrominance from the band-pass filtered
CVBS signal.
D
Compensates the internal processing time of the
band-pass filters and the chrominance comb filter section.
L
The comb filtered luminance output signal is obtained by
adding the delayed CVBS signal and the inverted comb
filtered chrominance signal.
1997 Mar 03
UMINANCE COMB FILTER
EXT
WITCHED CAPACITOR DELAY LINE
WITCHED CAPACITOR
HROMINANCE COMB FILTER
ELAY COMPENSATION
Integrated NTSC comb filter
(
PIN
PIN
PIN
PIN
14)
12)
13)
20)
B
AND
-P
ASS
F
ILTERS
(BPF
S
)
f
sc
)
6
L
Analog input low-pass filter to reduce the outband
frequencies of EMC. The input low-pass filter is included in
the signal path.
L
Two different types of output low-pass filters LPFO1 and
LPFO2 are necessary to get equal signal delays within the
luminance path and the chrominance path (important for
good transient behaviour). The low-pass output filter type
LPFO1 is used for the luminance output while LPFO2 is
used for the chrominance output. The filters are analog 3rd
order elliptic low-pass filters that convert the output signals
from the time discrete to the time continuous domain
(reconstruction filter).
LPF
Automatic tuning of the low-pass filters is achieved by
adjusting the filter delays. The control information for all
filters (CONT1 and CONT2) is derived from a built-in
reference filter (LPFO1-type) that is part of a control loop.
The control loop tunes the reference filter delay and thus
all other filter delays to a time reference derived from the
system clock CL3.
C
The control and clock processing block consists of the
sub-blocks PLL, clock processing and mode control. Only
if the input level at SVHS (pin 2) selects the COMB mode
the PLL and the clock processing are released for
operation.
Main tasks of the control and clock processing are:
The signal processing is based on a 3
(CL3), that is generated by the clock processing from the
f
correction of 180 is necessary every line because the
subcarrier frequency divided by the line frequency results
not in an integer value. Additionally the clock processing is
synchronized fieldwise by the H-signal (correction of line
frequency instabilities).
sc
OW
OW
ONTROL AND CLOCK PROCESSING
Clock generation of system clock CL3
Delay line start control
Mode control.
-signal at FSC (pin 1) via a PLL. A clock phase
-
-
CONTROL
PASS
PASS
F
F
ILTER
ILTER
I
O
NPUT
UTPUTS
(LPFI)
(LPFO1
Preliminary specification
(CLOCK CONTROL)
AND
LPFO2)
f
SAA4963
sc
system clock