TDA9112 datasheet(34/51 Pages) STMICROELECTRONICS

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TDA9112

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waveforms have no effect in the vertical middle of

the screen (if the

VPOS control is adjusted to its

medium value). As they are summed, the resulting

waveform tends to reach its maximum span at top

and bottom of the picture. The voltage at the

EWOut is top and bottom limited (see parameter

VEW). According to Figure 13, especially the bot-

tom limitation seems to be critical for maximum

horizontal size (minimum DC). Actually it is not

critical since the parabola component must always

be applied. As all the components of the resulting

correction waveform are generated from the out-

put vertical deflection drive waveform, they all

track with real vertical amplitude and position (in-

cluding breathing compensation), thus being fixed

vertically on the screen. They are also affected by

C- and S-corrections. The sum of components oth-

er than DC is affected by value in

HSIZE I2Cbus

control in reversed sense. Refer to electrical spec-

ifications for value. The DC value, adjusted via

HSIZE control, is also affected by voltage on HEH-

TIn input, thus providing a horizontal breathing

compensation (see electrical specifications for val-

ue). The resulting waveform is conditionally multi-

plied with voltage on HPLL1F, which depends on

frequency. Refer to electrical specifications for val-

ue and more precision. This tracking with frequen-

cy provides a rough compensation of variation of

picture geometry with frequency and allows to fix

the adjustment ranges of I

2C bus controls through-

out the operating range of horizontal frequencies.

It can be switched off by

EWTrHFr I2C bus bit (off

by default).

The EW waveform signal is buffered by an NPN

emitter follower, the emitter of which is directly

routed to EWOut output, with no internal resistor to

ground. It is to be biased externally.

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