III.2- I2C Control Adjustments
S and C correction shapes can then be added to
this ramp. These frequency independentS and C
corrections are generated internally. Their ampli-
tudesare adjustableby their respectiveI2C regis-
ters. Theycanalso be inhibitedby theirselect bits.
Finally, the amplitude of this S and C corrected
ramp can be adjusted by the vertical ramp ampli-
tudecontrol register.
Theadjusted ramp is availableon Pin23 (VOUT)to
drive an externalpower 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
I2C register (vertical position). Its value is
VPOS= 7/16 ⋅VREF-V ±300mV.
UsuallyVOUTis sentthrough a resistivedivider to
the inverting input of the booster. Since VPOS
derives from VREF-V, the bias voltage sent to the
non-invertinginput of the booster should also de-
rivefrom VREF-V to optimizethe accuracy(seeAp-
plicationDiagram).
III.3- VerticalMoiré
By using the vertical moiré, VPOS can be modu-
latedfromframeto frame.Thisfunctionis intended
tocancelthefringeswhichappearwhenlineto line
intervalis very close to the CRT vertical pitch.
The amplitude of the modulation is controlled by
register VMOIRE on sub-address 0C and can be
switched-offvia the control bit D7.
III.4- Basic Equations
Infirst approximation,the amplitudeoftherampon
Pin23 (VOUT) is :
VOUT -VPOS= (VOSC -V
DCMID)⋅(1 + 0.25(VAMP))
with:
-V
DCMID = 7/16 ⋅VREF (middle value of the ramp
on Pin22, typically 3.5V)
-V
OSC =V
22 (rampwith fixed amplitude)
-V
AMP = -1for minimumvertical amplituderegister
value and+1 formaximum
- VPOSis calculatedby : VPOS= VDCMID + 0.3VP
with VPequals -1 for minimum vertical position
registervalue and +1 for maximum
Thecurrent available on Pin 22 is :
IOSC =3
8⋅VREF ⋅COSC ⋅f
with: COSC : capacitorconnected on Pin 22 and
f : synchronizationfrequency.
III.5 - Geometric Corrections
The principle is representedin Figure 16.
Startingfromthe verticalramp,a parabola-shaped
currentisgeneratedforE/Wcorrection(alsoknown
as Pin Cushion correction), dynamic horizontal
phase control correction, and vertical dynamicFo-
cus correction.
The parabola generator is made by an analog
multiplier, the output current of which is equal to :
∆I=k⋅(VOUT -V
DCMID)2
where VOUTis thevertical outputramp (typically be-
tween2and5V)andVDCMIDis3.5V(forVREF-V =8V).
Onemoremultiplierprovidesa currentproportional
to (VOUT -V
DCMID)4for corner correction.
The VOUTsawtooth is typically centeredon 3.5V.
By changing the vertical position, the sawtooth
shiftsby ±0.3V.
Inordertohavegoodscreengeometryforany 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 thelarge 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 I2C registers
values.
FortheE/Wpartand the dynamichorizontalphase
controlpart,asawtooth-shapeddifferentialcurrent
in the followingform is generated:
∆I’ = k’ ⋅(VOUT -V
DCMID)
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
dynamichorizontalphasecontrolsmaybeinhibited
by their own I2C selectbit.
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 (10kΩto ground).
Sincestable in temperature,the devicecanbe DC
coupledwith an externalcircuitry.
The vertical dynamic focus is available on Pin 10.
The dynamic horizontalphase controldrives inter-
nally the H-position, moving the HFLYposition on
the horizontal sawtoothin the range of ±1.4% TH
both for side pin balance and parallelogram.
OPERATINGDESCRIPTION (continued)
TDA9109/SN
22/30