STV9118 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'STV9118' PDF : 46 Pages View PDF
STV9118
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 21
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 routed to
EWOut output, with an internal resistor to ground.
32/46
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