TDA9106 datasheet(24/30 Pages) STMICROELECTRONICS

24 / 30 page

III - VERTICAL PART

III.1 - Geometric Corrections

OPERATING DESCRIPTION (continued)

The principle is represented in Figure 21.

Starting from the vertical ramp, a parabola shaped

current is generated for E/W correction, dynamic

horizontal phase control correction, and vertical

dynamic Focus correction.

The base of the parabola generator is an analog

multiplier the output current of which is equal to :

∆I= k ⋅ (VOUT -VDCOUT)2

Where Vout is the vertical output ramp, typically

comprised between 2 and 5V, Vdcout is the vertical

DC output adjustable in the range 3.2V

≥ 3.8V in

order to generatea dissymetric parabolaif required

(keystone adjustment).

Corner and Corner Balance corrections may be

added to the E/W one. These are respectively 3rd

and 2nd order waveforms.

In order to keep a good screen geometry for any

end user preferences adjustment we implemented

the “geometry tracking”.

Due to large output stages voltage range (E/W,

FOCUS), the combination of tracking function with

maximum vertical amplitude max or min vertical

position and maximum gain on the DAC control

may lead to the output stages saturation. This must

be avoided by limiting the output voltage by apro-

priate I

2C registers values.

For E/Wpart and Dynamic Horizontal phase control

part, a sawtooth shaped differential current in the

following form is generated :

∆I’ = k’ ⋅ (VOUT -VDCOUT)2

Then

∆I and ∆I’ are added together and converted

into voltage for the E/W part.

Each of the four E/W components or the two Dy-

namic Horizontal phase control ones may be inhib-

ited by their own I

2C select bit.

The E/W parabolais availableon Pin 31 by the way

of an emitter follower which has to be biased by an

external resistor (10k

Ω). It can be DC coupled with

external circuitry.

The output connection of the vertical Dynamic Fo-

cus is the same as the E/W one.

This reverse parabola is available on Pin 32.

Dynamic Horizontal phase control current drives

internally the H-position, moving the Hfly position

on the Horizontal sawtooth in the range

± 2.8% Th

both on SidePin Balance and Parallelogram.

EW Output

EW amp

Keystone

Corner

Corner Balance

Sidepin amp

Parallelogram

Vertical Dynamic

Focus Output

Sidepin Balance

Output Current

To Horizontal

Phase

VDCOUT

VDCIN

VDCOUT

VMID

Vertical Ramp V

OUT

Vertical Ramp V

OSC

Figure 21 : Geometric Corrections Principle

TDA9106

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