Daewoo 14A5 Service Manual page 19

No Name
28 LUMINANCE
OUTPUT
29 B-Y OUTPUT
30 R-Y OUTPUT
31 B-Y INPUT
32 R-Y INPUT
33 SECAM REF
OUTPUT
34 X-TAL 3.58
35 X-TAL 4.43
36 LOOP FILTER
BURST PHASE
DETECTOR
38 CVBS OUTPUT
39 BLACK PEAK
HOLD CAPACITOR
40 HOR OUTPUT
41 SANDCASTLE
OUTPUT/
FLYBACK INPUT
42 PHI-2 FILTER /
FLASH PROTECT
Description
to the luminance input pin 27.
The pin is internally AC coupled to the luminance clamp via a capacitor of
50pF; clamping action occurs during burstkey period.
The luminance output signal is approximately l V black-white with typical
output impedance of 25O ohm.
The maximum output impedance of pins 29 and 30 is 500
signals are identified. When SECAM is identified by the SECAM add-on and
no PAL/NTSC is already identified by the ASM, then the ASM sets the
-(B-Y)/-(R-Y) output switch open (via DEMSW).
This enables the -(B-Y)/-(R-Y) outputs of the TDA8395 to be directly connected
to pins 29 and 3O respectively.
The -(B-Y),-(R-Y) output signals (supplied from baseband delay line) are AC
coupled, via a coupling capacitor of 10nF or greater, to the -(B-Y)/-(R-Y) inputs;
both inputs are clamped during burstkey period.
The SECAM reference output is directly connected to pin l of the TDA8395 for
SECAM decoding ; it also can be used as a reference for comb filter applications.
To ensure correct operation of both:
- colour processing internal circuits,
- sync calibration internal circuits,
it is only allowed to have 3.6MHz Xtals on pin34: both 4.4MHz,3.6MHz Xtals
are allowed on pin 35.
If pin 35 is not used: then it is left open in application (also XA,XB=O,1 ).
One of the important aspects of the PLL is the 1oop filter connected to pin 36;
it influences the dynamic performance of the loop.
The output amplitude is 1Vpp (transfer gain ratio between CVBS1int or
CVBS2ext or CVBS3ext/Ys-vhs and CVBSout is 1).
The maximum output impedance is 250 ohm.
For the correct working of the black stretcher an external time constant should
be added at the black peak hold capacitor input.
This open collector output is meant to drive the horizontal output stage.
The output is active low, i.e. the line transistor should conduct during the low
period of the output.
Pin 41 is a combined input/output pin.
The pin provides a three level sandcastle pulse.
Both burstkey pulse and vertical blanking pulse are always available, the line
blanking pulse is only present when the external flyback pulse is fed to this pin.
The line flyback pulse, fed to this pin is used for two functions:
- input signal for the PHI-2 1oop and
- RGB line blanking. (without flyback pulse blanking occurs only during the
burstkey pulse)
To ensure correct working of the delay line and SECAM add-on, the output
should not be loaded with more than:
- Sandcastle input delay line TDA 4665
- Sandcastle input SECAM add-on TDA 8395
The loopfilter is a first order filter.
This pin requires a capacitor (C) only.
19
when PAL/NTSC