TDA9109SN datasheet(22/30 Pages) STMICROELECTRONICS

22 / 30 page

III.2 - I

2C Control Adjustments

S and C correction shapes can then be added to

this ramp. These frequency independent S and C

corrections are generated internally. Their ampli-

tudes are adjustable by their respective I

2C regis-

ters. They can also be inhibited by their select bits.

Finally, the amplitude of this S and C corrected

ramp can be adjusted by the vertical ramp ampli-

tude control register.

The adjusted ramp is available on Pin 23 (VOUT)to

drive an external power stage.

The gain of this stage can be adjusted (

±25%)

dependingon its register value.

The mean value of this ramp is driven by its own

2C register (vertical position). Its value is

VPOS = 7/16

⋅ VREF-V ± 300mV.

Usually VOUT is sent through a resistive divider to

the inverting input of the booster. Since VPOS

derives from VREF-V, the bias voltage sent to the

non-inverting input of the booster should also de-

rive from VREF-V to optimize the accuracy (see Ap-

plication Diagram).

III.3 - Vertical Moiré

By using the vertical moiré, VPOS can be modu-

lated from frame to frame. This function is intended

to cancel the fringes which appear when line to line

interval is very close to the CRT vertical pitch.

The amplitude of the modulation is controlled by

switched-off via the control bit D7.

III.4 - Basic Equations

In first approximation, the amplitude of the ramp on

Pin 23 (VOUT) is :

VOUT - VPOS = (VOSC -VDCMID)

⋅ (1 + 0.25 (VAMP))

with :

-VDCMID = 7/16

⋅ VREF (middle value of the ramp

on Pin 22, typically 3.5V)

-VOSC =V22 (ramp with fixed amplitude)

-VAMP = -1 for minimum vertical amplitude register

value and +1 for maximum

- VPOS is calculated by : VPOS = VDCMID + 0.3 VP

with VP equals -1 for minimum vertical position

The current available on Pin 22 is :

IOSC

⋅ VREF ⋅ COSC ⋅ f

with : COSC : capacitor connected on Pin 22 and

f : synchronization frequency.

III.5 - Geometric Corrections

The principle is represented in Figure 16.

Starting from the vertical ramp, a parabola-shaped

current is generatedfor E/W correction (also known

as Pin Cushion correction), dynamic horizontal

phase control correction, and vertical dynamic Fo-

cus correction.

The parabola generator is made by an analog

multiplier, the output current of which is equal to :

∆I= k ⋅ (VOUT -VDCMID)2

where VOUT is the vertical output ramp (typically be-

tween2 and5V)andVDCMID is 3.5V(forVREF-V =8V).

One more multiplier provides a current proportional

to (VOUT -VDCMID)

4 for corner correction.

The VOUT sawtooth is typically centered on 3.5V.

By changing the vertical position, the sawtooth

shifts by

±0.3V.

In order to have good screen geometry for any end

user adjustment, the TDA9109/SN has the ”ge-

ometry tracking” feature, which allows generation

of a dissymetric parabola depending on the verti-

cal position.

Due to the large output stage voltage range (E/W,

Keystone, Corner), the combination of tracking

function with maximum vertical amplitude, maxi-

mum or minimum vertical position and maximum

gain on the DAC control may lead to the output

stage saturation. This must be avoided by limiting

the output voltage with apropriate I

2C registers

values.

For the E/W part and the dynamic horizontal phase

control part, a sawtooth-shapeddifferential current

in the following form is generated :

∆I’ = k’ ⋅ (VOUT -VDCMID)

Then

∆I and ∆I’ are added and converted into

voltage for the E/W part.

Each of the three E/W components, and the two

dynamichorizontal phasecontrols may be inhibited

by their own I

2C select bit.

The E/W parabola is available on Pin 24 via an

emitter follower output stage which has to be bi-

ased by an external resistor (10k

Ω to ground).

Since stable in temperature, the device can be DC

coupled with an external circuitry.

The vertical dynamic focus is available on Pin 10.

The dynamic horizontal phase control drives inter-

nally the H-position, moving the HFLY position on

the horizontal sawtooth in the range of

± 1.4% TH

both for side pin balance and parallelogram.

OPERATING DESCRIPTION (continued)

TDA9109/SN

22/30

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