TDA8357 Philips Semiconductors, TDA8357 Datasheet - Page 10

• Manufacturer Part Number: TDA8357
• Description: Full bridge vertical deflection output circuit in LVDMOS
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Supply voltage calculation
For calculating the minimum required supply voltage,
several specific application parameter values have to be
known. These parameters are the required
maximum (peak) deflection coil current I
parameters R
of R
current should also include the overscan.
The deflection coil resistance has to be multiplied with 1.2
in order to take account of hot conditions.
Chapter “Characteristics” supplies values for the voltage
losses of the vertical output stage. For the first part of the
scan the voltage loss is given by V
part of the scan the voltage loss is given by V
The voltage drop across the deflection coil during scan is
determined by the coil impedance. For the first part of the
scan the inductive contribution and the ohmic contribution
to the total coil voltage drop are of opposite sign, while for
the second part of the scan the inductive part and the
ohmic part have the same sign.
For the vertical frequency the maximum frequency
occurring must be applied to the calculations.
The required power supply voltage V
the scan is given by:
The required power supply voltage V
of the scan is given by:
The minimum required supply voltage V
highest of the two values V
voltage and component values also has to be taken into
account.
Flyback supply voltage calculation
If the flyback time is known, the required flyback supply
voltage can be calculated by the simplified formula:
where:
1999 Nov 10
V
V
V
x
–
+
P 1
P 2
FB
Full bridge vertical deflection output circuit
in LVDMOS
L
=
L
coil
coil
M
-------------------------- -
R
=
. The required maximum (peak) deflection coil
=
=
coil
I
L
I
coil p p
coil peak
I
2I
2I
coil
coil peak
+
coil peak
coil peak
R
–
coil
M
and L
R
-------------------------- -
1 e
coil
–
R
R
f
f
coil
coil
vert max
vert max
coil
t –
+
FB
, and the measuring resistance
R
+
P(1)
+
M
x
R
R
M
M
and V
+
+
V
V
loss(1)
loss 1
loss 2
P(2)
P
P
for the second part
for the first part of
. Spread in supply
. For the second
P
coil(peak)
shall be the
loss(2)
, the coil
.
10
The flyback supply voltage calculated this way is about
5% to 10% higher than required.
Calculation of the power dissipation of the vertical
output stage
The IC total power dissipation is given by the formula:
P
The power to be supplied is given by the formula:
In this formula 0.3 [W] represents the average value of the
losses in the flyback supply.
The average external load power dissipation in the
deflection coil and the measuring resistor is given by the
formula:
Example
Table 1 Application values
Table 2 Calculated values
P
P
I
I
L
R
R
f
t
V
R
t
x
V
P
P
P
tot
coil(peak)
coil(p-p)
vert
FB
vert
sup
L
coil
P
FB
sup
L
tot
coil
M
M
= P
=
+ R
SYMBOL
SYMBOL
=
------------------------------- -
I
sup
coil peak
coil
V
P
(hot)
3
P
I
----------------------- -
L
coil peak
2
2
0.725
1.45
8.82
7.9
1.5
50
640
11
11
0.02
0.000802
29
4.45
1.93
2.52
R
+
coil
VALUE
VALUE
V
P
+
R
0.015 [A]
M
Preliminary specification
TDA8357J
A
A
mH
Hz
V
s
V
W
W
W
+
s
0.3 [W]
UNIT
UNIT