SAA4960 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

SAA4960

Integrated PAL comb filter

Philips Electronics 

Philips Semiconductors

Integrated PAL comb filter

Preliminary specification

SAA4960

FUNCTIONAL DESCRIPTION

Functional requirements

The PAL comb filter processes the video standards PAL B,

G and H. 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 four pins:

1. BYP forces the IC into the BYPASS-mode (comb filter

function off)

2. SSYN defines whether the COMB-mode is entered

synchronously or not and defines the polarity of the

BYP pin

3. FSCSW selects the reference frequency fsc or 2 × fsc

4. LPFION enables the internal pre-filter.

It is possible to select the following modes of operation:

COMB-mode: Luminance and chrominance comb filter

function active if BYPASS-mode not active.

BYPASS-mode: Signal processing not active, all clocks

inactive, Cext (pin 10) is bypassed to CO (pin 12) and

Yext/CVBS (pin 17) is bypassed to YO (pin 14) and

CVBSO (pin 15). This mode is forced via BYP (pin 3).

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

MODE CHANGE

COMB-mode to BYPASS-mode

BYPASS-mode to COMB-mode

MAXIMUM

STABILIZATION

TIME

1 line

1 field

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.

Pin description

FSC (PIN 1)

Input for the reference frequency fsc (see note 2 of Chapter

“Characteristics”) or 2 × fsc. For SECAM standard signals

the best signal performance in BYPASS-mode is achieved

by switching the FSC input signal off externally.

BYP (PIN 3)

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.

Dependent on SSYN the BYP input can be either inverted

or non-inverted with the function as shown in Table 2:

Table 2 Bypass function

SSYN BYP

LOW LOW

LOW HIGH

HIGH LOW

HIGH HIGH

SELECTED MODE

COMB-mode

BYPASS-mode

BYPASS-mode

COMB-mode

Dependent 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

SSYN

ENTERING COMB-MODE

LOW immediately if BYP = LOW

HIGH synchronized by vertical pulse if BYP = HIGH

The PLL and the clock processing are always stopped if

the selected level for BYPASS is applied to BYP

(independent of the vertical pulse).

1996 Oct 15

5

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