TDA9116 datasheet(33/47 Pages) STMICROELECTRONICS

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TDA9116

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10.5 - EW DRIVE SECTION

The goal of the EW drive section is to provide, on

pin EWOut, a waveform which, used by an exter-

nal DC-coupled power stage, serves to compen-

sate for those geometry errors of the picture that

are symmetric versus vertical axis across the mid-

dle of the picture.

The waveform consists of an adjustable DC value,

corresponding to horizontal size, a parabola of 2nd

order for “pin cushion” correction, a linear for “key-

stone” correction and independent half-parabolas

of 4th order for top and bottom corner corrections.

All of them are adjustable via I2C bus, see I2C

BUS CONTROL REGISTER MAP on page 22

chapter.

Refer to Figure 12, Figure 13 and to chapter TYP-

ICAL OUTPUT WAVEFORMS. The correction

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 I2C bus

control in reversed sense. Refer to electrical spec-

ifications for value. The DC value, adjusted via

HSIZE control, is also affected by voltage on HE-

HTIn 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 I2C 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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