TDA9109 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TDA9109' PDF : 30 Pages View PDF
TDA9109/SN
OPERATING DESCRIPTION (continued)
III.2 - I2C 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 I2C 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
I2C 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
register VMOIRE on sub-address 0C and can be
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
register value and +1 for maximum
The current available on Pin 22 is :
IOSC
=
3
8
⋅
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
currentis 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 currentproportional
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 I2C 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 phasecontrolsmay be inhibited
by their own I2C 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 (10kΩ 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.
22/30
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