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AN1290 Vertical
Section
5.1.8
Vertical Signal Management in the TDA9112A
The block diagram of the vertical signal has been greatly modified in the TDA9112A in order to
obtain the following improvements:
●
“Tracking” of S and C linearity corrections: linearity of the display will remain unaffected when
changing V size and position;
●
Perfect fit of S correction to all tube types;
●
No influence of linearity corrections on the E/W corrections;
●
Adaptation to various tubes by I²C only.
The block diagram is represented in
The signal from ramp generator, modified for the suppression of parasitic E/W parabola, is first sent
to a variable gain amplifier (for vertical amplitude setting), then a variable offset is added for vertical
position control.
The resulting Vramp is used to generate the S and C correction signals, and, further, the E/W
corrections. Since the corrections depend only on the present value of the ramp (i.e. on the present
value of scanning current), they will remain fixed on the screen while amplitude and position are
adjusted. This is the “tracking” feature.
Adjusting S compensation will not influence the display amplitude if the amplitude setting is
medium, for other settings there will be some influence.
Figure 10: Vertical Waveform
Waveform on pin 22
Waveform for following stages
