tda8433 NXP Semiconductors, tda8433 Datasheet - Page 19

• Manufacturer Part Number: tda8433
• Description: Deflection Processor For Computer Controlled Tv Receivers
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Vertical drive waveform
The vertical drive waveform has
certain interactions between the
parameters whereby:
The alignment can be made
non-repetitive. Once correct values
for the V-S correction and V-linearity
are set, the picture height may be
changed without affecting the V-S
correction and V-linearity on the
screen.
The formula for the vertical drive
waveform at pin 21 is:
V
(1
Picture height
The amplitude of the sawtooth
waveform is controlled by 'A'. It
follows therefore that:
0.53
V-linearity
This function is meant to compensate
for non-linearity of AC coupled
vertical output stages. The linearity
correction changes proportionally to
the picture height setting. The range
for linearity control is typically 17% of
August 1991
The nominal value for 'A' is found for
a = 0.5, therefore A = 0.67. By
programming the picture height, the
sawtooth amplitude can be adjusted
from 19% to +19%. Without
S-correction (S = O) and linearity
correction (Y = O), the nominal
sawtooth amplitude is (with A = 0.67);
1.32 x 0.67 x 2 = 1.77 V
vert
The S-correction influences the
picture height
The linearity correction can
influence the picture shift.
Deflection processor for computer
controlled TV receivers
VE) + YZ
= D + 1.32 A {(Z
A
0.8
2
} volts.
SA
(p-p)
2
Z
3
)
the peak-to-peak value of the linear
sawtooth (see Fig.7).
V-S correction
The range for the V-S correction
(SA
the undistorted peak-to-peak
sawtooth voltage (see Fig.7). The
actual S-correction component (SA
is dependent on the picture height
setting where:
At maximum picture height (A = 0.80)
: SA
At nominal picture height (A = 0.62) :
SA
At minimum picture height (A = 0.53)
: SA
Picture shift
The DC level of the output is fixed by
'D'. It can be adjusted within a range
of 19% to +19%. In actual
application this will be used for
shifting the picture vertically.
V-compensation
The vertical deflection can be
modulated by the instantaneous
value of the signal applied to the EHT
compensation input. This external
signal should reflect the EHT
variations. The amount of deflection
reduction is in the range 0 to 10%, if
pin 24 is at (V
(maximum modulation i.e. 1.7 V
typical). Thus for maximum
modulation, the V-drive waveform
can be reduced to 90% of its value.
There is no reduction when the
EHT-compensation input is at
V
CC
2
2
2
2
= 0.197
/ 2 V (i.e. 6 V typical).
) is defined as a percentage of
= 0.282
= 0.125
CC
/ 2)
19
4.3 V
2
)
Trapezium
The trapezium function is the only
IC-confined adjustment and is
intended to compensate for any
internal offsets. The function is called
Trapezium because of its effect on
the picture if an AC-coupled vertical
deflection stage is used. The
trapezium function can alter the
picture shift range by a maximum of
190 mV. If the trapezium function is
used for purposes other than
eliminating the internal offsets, then
the V-linearity can affect the actual
picture height. This can affect the
symmetry of the S-correction which,
in turn, can affect the V-linearity.
E-W drive waveform
In order to obtain independent control
of the picture width, parabola function
and the H-compensation on a screen
each function has been designed to
be dependent on the other two. With
reference to Fig.8, the voltage across
the H-deflection stage is:
V
Where:
This shows for instance, that the
H-compensation is made dependent
on the actual value of the parabola
function. For a TV set which needs a
large parabola compensation and,
also, a large EHT-compensation, this
function allows an optimal
EHT-compensation independent of
the parabola function.
V
W
P
E
def1
supply
= V
supply
= supply voltage for
H-deflection stage
= picture width alignment
= parabola function
= H-compensation
(1
Product specification
W) (1
TDA8433
P) (1
E)