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STMicroelectronics Confidential
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AN1290
Special Features of the TDA9112A
2
Special Features of the TDA9112A
The TDA9112A provides features and performances at least equal to those of the TDA9112, with
one exception: the DC/DC converter configuration using an internal oscillator has not been
continued because very few customers used it. Software compatibility is maintained.
The new or improved functions are listed below and details may be found in the relevant chapters.
The most important improvements concern geometry and focus correction.
Control
●
8-bit control of the H-size and H-position. Compatibility with the rest of the family is maintained
since only the LSB is affected.
●
A dedicated bit enables the MCU to automatically detect whether the circuit present is the
TDA9112 or the TDA9112A.
Horizontal
●
In PLL1, now there is a choice between 4 values of the charge-pump current, to better optimize
jitter in relation to the horizontal frequency.
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The indication of H-frequency Unlock can be made twice as fast as previously.
Vertical
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The block diagram of S and C linearity corrections has been modified to fit in the “tracking”
feature. As a result, it is possible to adjust amplitude or to switch between the VGA modes
without impairing linearity.
●
The law of S correction has been modified, allowing perfect fitting to various types of tubes.
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Further to regular amplitude and centring settings (which maintain ideal linearity and
pincushion correction thanks to the “tracking” feature), the new prescale settings (without
tracking feature) provide better flexibility, for instance to adapt one chassis to various tubes.
●
New EHT compensation has a two-quadrant sensitivity adjustment (i.e. you can choose the
compensation sign as well). This allows perfect compensation throughout the H-frequency
range.
East/West Pin Cushion Correction and Advanced Geometry Corrections
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Two new controls of E/W are provided, namely S and W control. Their action is symmetrical
versus center. They leave top, bottom and middle of the screen unaffected:
— S correction inflates the top 1/4 and deflates the bottom 3/4 or the opposite,
— W correction inflates top 1/4 and bottom 3/4, or deflates both.
These corrections may help prevent certain distortions related to the DC/DC converter.
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A control bit can disable the tracking of E/W corrections versus H-amplitude.
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New EHT compensation has a two-quadrant sensitivity adjustment, independent of the one for
the Vertical section.