TDA935x Philips, TDA935x Datasheet - Page 62

• Manufacturer Part Number: TDA935x
• Description: TV Signal Processor-Teletext Decoder with Embedded u-Controller
• Manufacturer: Philips

Philips Semiconductors
Audio circuit and input signal selection
The audio control circuit contains an audio switch with 1
external input and a volume control circuit. The selection
of the various inputs is made by means of the ADX bit. In
various versions the Automatic Volume Levelling (AVL)
function can be activated. The pin to which the external
capacitor has to be connected depends on the IC version.
For the 90 types the capacitor is connected to the EW
output pin. For the 110 types a choice must be made
between the AVL function and a sub-carrier output for
comb filter applications. This choice is made via the
CBM0/1 bits (in subaddress 22H). When the AVL is active
it automatically stabilises the audio output signal to a
certain level.
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.
2001 Jan 18
TV signal processor-Teletext decoder with
embedded -Controller
VIDEO IDENT
IDENT
Fig.27 CVBS switch and interfacing of video ident
VIM
CVBS1
CVBS2/Y
62
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.
C
TDA935X/6X/8X PS/N2 series
TO CHROMA PROCESSING
TO LUMA/SYNC PROCESSING
Tentative Device Specification
SVO
IFVO/SVO
(+)
IFVO