STV9118 datasheet(31/46 Pages) STMICROELECTRONICS

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STV9118

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The frequency range in which the AGC loop can

regulate the amplitude also depends on this ca-

pacitor.

The C- and S-corrections of shape serve to com-

pensate for the vertical deflection system non-line-

arity. They are controlled via

CCOR and SCOR

I2C bus controls.

Shape-corrected sawtooth with regulated ampli-

tude is lead to amplitude control stage. The dis-

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

compensate for spread of VRefO value (and so

mean output value) between particular devices.

10.4.2 - 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 half-frame

frequency. 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,.

Figure 11. Vertical section block diagram

Synchro

Polarity

Controller

Discharge

Sampling

Capacitance

S-correction

CCOR

C-correction

VVOB

sawtooth

REF

Charge current

Transconductance amplifier

(I2C)

SCOR (I2C)

20 VAGCCap

discharge

CCOR

VSIZE (I2C)

VMOIRE (I2C)

VPOS (I2C)

VOscF

VOut

VEHTIn

VCap

VSyn

OSC

Cap.

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