TDA9115 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9115' PDF : 45 Pages View PDF
TDA9115
charge exponential is replaced by VVOB level,
which, under control of the CONTROLLER, cre-
ates a rapid falling edge and a flat part before be-
ginning of new ramp. Mean value of the waveform
output on pin VOut is adjusted by means of VPOS
I2C bus control, its amplitude through VSIZE I2C
bus control. Vertical moiré is superimposed.
The biasing voltage for external DC-coupled verti-
cal power amplifier is to be derived from VRefO
voltage provided on pin RefOut, using a resistor di-
vider, this to ensure the same temperature drift of
mean (DC) levels on both differential inputs and to
Figure 11. Vertical section block diagram
compensate for spread of VRefO value (and so
mean output value) between particular devices.
9.4.2 Vertical moiré
To blur the interaction of deflection lines with CRT
mask grid pitch that can generate moiré pattern,
the picture position is to be alternated at frame fre-
quency. For this purpose, a square waveform at
half-frame frequency is superimposed on the out-
put waveform’s DC value. Its amplitude is adjusta-
ble through VMOIRE I2C bus control,.
Charge current
Transconductance amplifier
VSyn 2
Synchro
Polarity
OSC
Cap.
VCap
22
Discharge
Controller
Q1
REF
Sampling
sawtooth
discharge
20 VAGCCap
Sampling
Capacitance
S-correction
SCOR (I2C)
CCOR (I2C)
C-correction
18 VEHTIn
19
VOscF
VVOB VSIZE (I2C)
VMOIRE (I2C)
VPOS (I2C)
23 VOut
9.5 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 and a linear for
“keystone” correction. All of them are adjustable
via I2C bus, see I2C BUS CONTROL REGISTER
MAP on page 20.
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-
29/45
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