TDA9554PS datasheet(64/125 Pages) PHILIPS

64 / 125 page

2000 Jun 22

Philips Semiconductors

Tentative Device Speciﬁcation

TV signal processor-Teletext decoder with

embedded

µ-Controller

TDA955X/6X/8X PS/N1 series

It is possible to use the deemphasis pin as additional audio

input. In that case the internal signal must, of course, be

switched off. This can be realised by means of the sound

mute bit (SM in subaddress 29H). When the IF circuit is

switched to positive modulation the internal signal on the

deemphasis pin is automatically muted.

CVBS and Y/C input signal selection

The circuit has 2 inputs for external CVBS signals and one

input can also be used as one Y/C input (see Fig. 27).

It is possible to supply the selected CVBS signal to the

demodulated IF video output pin. This mode is selected by

means of the SVO bit in subaddress 22H. The vision IF

amplifier is switched off in this mode.

The video ident circuit can be connected to the incoming

‘internal’ video signal or to the selected signal. This ident

circuit is independent of the synchronisation and can be

used to switch the time-constant of the horizontal PLL

depending on the presence of a video signal (via the VID

bit). In this way a very stable OSD can be realised.

The subcarrier output is combined with a 3-level output

switch (0 V, 2.3 V and 4.5 V). The output level and the

availability of the subcarrier signal is controlled by the

CMB1 and CMB0 bits. The output can be used to switch

sound traps etc. It is also possible to use this pin for the

connection of the AVL capacitor or as AM output.

TO LUMA/SYNC PROCESSING

TO CHROMA PROCESSING

CVBS2/Y

CVBS1

VIM

VIDEO IDENT

IDENT

Fig.27 CVBS switch and interfacing of video ident

(+)

IFVO

IFVO/SVO

SVO

Synchronisation circuit

The IC contains separator circuits for the horizontal and

vertical sync pulses and a data-slicing circuit which

extracts the digital teletext data from the analog signal.

The horizontal drive signal is obtained from an internal

VCO which is running at a frequency of 25 MHz. This

oscillator is stabilised to this frequency by using a 12 MHz

signal coming from the reference oscillator of the

µ-Controller/Teletext decoder.

The horizontal drive is switched on and off via the soft

start/stop procedure. This function is realised by means of

variation of the TON of the horizontal drive pulses. In

addition the horizontal drive circuit has a ‘low-power

start-up’ function.

The vertical synchronisation is realised by means of a

divider circuit. The vertical ramp generator needs an

external resistor and capacitor. For the vertical drive a

differential output current is available. The outputs must be

DC coupled to the vertical output stage.

In the types which are intended for 90

° picture tubes the

following geometry parameters can be adjusted:

• Horizontal shift

• Vertical amplitude

• Vertical slope

• S-correction

• Vertical shift

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