saa4961 NXP Semiconductors, saa4961 Datasheet - Page 5

• Manufacturer Part Number: saa4961
• Description: Saa4961 Integrated Multistandard Comb Filter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
Functional requirements
The multistandard comb filter processes the video
standards PAL B, G, H, M, N and NTSC M. PAL D and I
signals can also be processed but with the drawback of a
slightly reduced bandwidth.
For SECAM and SVHS signals the input signals can be
bypassed to the output without processing by selecting the
BYPASS-mode.
A sync separation circuit is incorporated to generate
control signals for the internal clock processing. With a
sync compression of up to 12 dB the sync separator works
properly (see Fig.4).
The IC is controlled via six pins:
1. BYP forces the IC into the BYPASS-mode (comb filter
2. SSYN defines whether the COMB-mode is entered
3. SYS1 selects the video standard
4. SYS2 selects the video standard
5. FSCSW selects the reference frequency f
6. LPFION enables the internal pre-filter.
It is possible to select the following modes of operation:
If the stimulus of the mode is changed, the IC is following
the new mode after the stabilization time given in Table 1.
Table 1 Stabilization time after mode change
The mode change from BYPASS to COMB depends on
SSYN (pin 6) and can be asynchronous or synchronous
related to the vertical pulse. The mode change from
COMB to BYPASS is always performed asynchronously.
1997 Feb 03
COMB-mode to BYPASS-mode
BYPASS-mode to COMB-mode
COMB-mode: luminance and chrominance comb filter
function active if BYPASS-mode not active.
BYPASS-mode: signal processing not active, all clocks
inactive, C
Y
CVBSO (pin 15). This mode is forced via BYP (pin 3).
Integrated multistandard comb filter
ext
function off)
synchronously or not and defines the polarity of the
BYP pin
/CVBS (pin 17) is bypassed to Y
MODE CHANGE
ext
(pin 10) is bypassed to C
STABILIZATION
O
MAXIMUM
(pin 14) and
O
1 field
(pin 12) and
TIME
1 line
sc
or 2
f
sc
5
Pin description
FSC (
Input for the reference frequency f
“Characteristics”) or 2
the best signal performance in BYPASS-mode is achieved
by switching the FSC input signal off externally.
BYP (
Input signal that controls the operation mode. A low-pass
filter is added to the input for suppression of subcarrier
frequencies. Thus applications are supported where the
operation mode (COMB or BYPASS) is controlled by the
DC-level of the FSC input signal at pin 1. For those
applications the BYP input can be externally connected to
FSC (pin 1).
Depending on SSYN (pin 6) the function of BYP can be
adapted to a certain application with respect to the polarity
of the logic level and with respect to the behaviour when
entering the COMB-mode.
Depending on SSYN the BYP input can be either inverted
or non-inverted with the function as shown in Table 2.
Table 2 Bypass function
Depending on SSYN the behaviour when entering the
COMB-mode is different for the both selectable logic
polarities while the BYPASS-mode is always entered
asynchronously (immediately).
Table 3 Behaviour when entering the COMB-mode
The PLL and the clock processing are always stopped if
the selected level for BYPASS is applied to BYP
(independent of the vertical pulse).
LOW
LOW
HIGH
HIGH
LOW
HIGH
SSYN
SSYN
PIN
PIN
1)
3)
LOW
HIGH
LOW
HIGH
immediately if BYP = LOW
synchronized by vertical pulse if
BYP = HIGH
BYP
ENTERING COMB-MODE
f
sc
. For SECAM standard signals
COMB-mode
BYPASS-mode
BYPASS-mode
COMB-mode
sc
Preliminary specification
SELECTED MODE
(see note 2 of Chapter
SAA4961